Cardiovascular

Acute myocarditis: workup and supportive management

Clinical Overview and When to Suspect Acute Myocarditis

— Most common cause in North America/Europe: viral (parvovirus B19, HHV-6, enteroviruses including coxsackie B, adenovirus, SARS-CoV-2, influenza)

— Post-vaccination myocarditis: mRNA COVID vaccines, especially young males age 16–30, typically 2–4 days after 2nd dose

— Immune checkpoint inhibitor (ICI) myocarditis: ipilimumab, nivolumab, pembrolizumab — high mortality, often within 6 weeks of initiation

— Other: Lyme carditis (endemic regions, AV block), Chagas (Latin America), giant cell myocarditis, eosinophilic (DRESS, hypereosinophilic syndromes), sarcoidosis, peripartum, cocaine, SLE, rheumatic fever

— Young/middle-aged patient with new chest pain, dyspnea, or new heart failure within days–weeks of a viral prodrome (URI, GI illness)

— Troponin elevation without obstructive CAD on angiography

— New unexplained arrhythmia, syncope, or LV dysfunction in a previously healthy adult

— Athlete with syncope or sudden cardiac arrest — myocarditis is a leading cause

— Chest pain mimicking ACS or pericarditis (myopericarditis)

— New-onset HF (days–weeks)

— Arrhythmia-predominant (VT, AV block — think Lyme, sarcoid, giant cell)

— Fulminant: shock requiring inotropes/MCS

Board pearl: A young patient with a recent viral illness, pleuritic chest pain, diffuse ST elevation, and elevated troponin should make you think myopericarditis, not STEMI — but you must still rule out ACS with imaging or cath if risk factors are present.

Definition: Inflammation of the myocardium causing myocyte injury, often with edema, necrosis, and contractile dysfunction; spectrum ranges from subclinical troponin elevation to fulminant cardiogenic shock.

Epidemiology and etiology:

When to suspect on Step 3:

Clinical syndromes:

Presentation Patterns and Key History

— Chest pain syndrome (myopericarditis): sharp, pleuritic, positional, worse supine/better leaning forward; mimics pericarditis but with troponin elevation

— Acute heart failure: dyspnea, orthopnea, PND, edema, fatigue over days to weeks

— Cardiogenic shock (fulminant): hypotension, cool extremities, end-organ hypoperfusion — paradoxically has better long-term recovery if patient survives the acute phase

— Arrhythmia/conduction: palpitations, syncope, new AV block, sustained VT

— Recent viral illness, COVID infection or mRNA vaccination (within 1 month)

— New medications: ICIs, clozapine, sulfonamides, anticonvulsants (eosinophilic/hypersensitivity)

— Travel/exposure: tick bite or hiking in NE US (Lyme), Latin America (Chagas), raw meat (Trichinella)

— Substance use: cocaine, methamphetamine, anabolic steroids

— Recent pregnancy/postpartum (peripartum cardiomyopathy — last month of pregnancy through 5 months postpartum)

— Autoimmune disease (SLE, sarcoid, IBD), prior thymoma (giant cell association)

— Family history of sudden death or cardiomyopathy

— Rapid progression of HF over hours–days

— Sustained VT or high-grade AV block

— Need for vasopressors

Step 3 management: When a patient on a checkpoint inhibitor presents with even mild dyspnea, fatigue, or troponin bump, hold the ICI immediately, get ECG/troponin/echo, and consult cardio-oncology — ICI myocarditis has 25–50% mortality and demands high-dose corticosteroids urgently.

Classic prodrome: 1–2 weeks of viral symptoms (fever, myalgias, URI, gastroenteritis) preceding cardiac symptoms — present in ~60% but absence does not exclude myocarditis.

Four dominant clinical pictures:

Targeted history — must-ask items:

Red flag features suggesting fulminant or giant cell:

Physical Exam Findings and Hemodynamic Assessment

— Sinus tachycardia out of proportion to fever is a classic clue

— Hypotension, narrow pulse pressure → shock

— Fever may persist from underlying viral illness

— S3 gallop (volume overload, reduced compliance)

— S4 if diastolic dysfunction predominates

— Soft S1 with severe LV dysfunction

— New murmur of functional MR from annular dilation

— Pericardial friction rub if myopericarditis (best at left lower sternal border, leaning forward, end-expiration)

— Cannon A waves, variable S1 → AV dissociation

— Bradycardia + erythema migrans rash → Lyme carditis

— Warm & wet: congestion without hypoperfusion → diuresis

— Cold & wet: congestion + hypoperfusion → inotropes ± diuresis, consider MCS

— Cold & dry: hypoperfusion without congestion → cautious fluids, inotropes

— Globally reduced LV systolic function, regional wall motion abnormalities can mimic ACS

— Pericardial effusion (small to moderate)

— IVC plethora supporting elevated RA pressure

CCS pearl: In a hypotensive myocarditis patient, don't reflexively bolus 2 L of saline. Get a quick echo or POCUS first — if EF is severely reduced and IVC is dilated, you'll precipitate pulmonary edema. Start low-dose inotrope (dobutamine or milrinone) and titrate.

General appearance: ranges from well-appearing (chest pain phenotype) to ill, diaphoretic, mottled (fulminant). Always assess perfusion early.

Vital signs:

Cardiac exam:

Pulmonary: bibasilar crackles, decreased breath sounds if pleural effusion

Peripheral signs of HF: JVD, hepatojugular reflux, hepatomegaly, ascites, pitting edema, cool extremities

Conduction-disease clues:

Hemodynamic profiling (Stevenson/Forrester):

Bedside ultrasound (POCUS):

Diagnostic Workup — Initial Labs, ECG, Imaging, Biomarkers

— Sinus tachycardia (most common)

— Diffuse concave ST elevation + PR depression (myopericarditis pattern)

— Pseudo-infarct patterns: focal ST elevation, Q waves — can mimic STEMI

— New AV block (1°, 2°, or complete) — think Lyme, sarcoid, giant cell, diphtheria

— Low voltage, electrical alternans → significant pericardial effusion

— Prolonged QRS or QTc — poor prognostic marker

— Troponin I/T elevated in most clinically apparent cases; degree correlates with myocyte injury

— Trend troponin q6–8h initially

— BNP/NT-proBNP elevated proportional to HF severity

— Eosinophilia → eosinophilic myocarditis (DRESS, parasites, hypereosinophilic syndrome)

— Lymphocytosis with atypical lymphocytes → viral

— COVID-19 PCR, influenza, Lyme serology if endemic exposure, HIV, Chagas if from endemic region

— Blood cultures if febrile (rule out endocarditis)

— Global or regional LV systolic dysfunction, increased wall thickness from edema, pericardial effusion, mural thrombus

— Establishes baseline EF and assesses RV function

Board pearl: A patient with chest pain, troponin rise, and an ECG suggestive of STEMI but clean coronaries on angiography = MINOCA workup, and myocarditis is the leading diagnosis — confirm with cardiac MRI.

ECG (do first, within 10 min of presentation):

Cardiac biomarkers:

Inflammatory markers: CRP, ESR elevated; not diagnostic but helpful for trending

CBC with differential:

CMP, LFTs, lactate: assess end-organ perfusion; transaminitis/lactate elevation → shock

TSH, HIV, iron studies to rule out reversible cardiomyopathy mimics

Viral/infectious workup (targeted, not shotgun):

CXR: may show cardiomegaly, pulmonary edema, or be normal early

Transthoracic echocardiography (TTE) — must obtain early:

Diagnostic Workup — Advanced and Confirmatory Studies

— Updated Lake Louise Criteria (2018): requires at least one T2-based marker (edema) AND one T1-based marker (non-ischemic injury — LGE, native T1 elevation, or increased ECV)

— Patchy mid-myocardial or subepicardial late gadolinium enhancement (LGE) — distinguishes from ischemic (subendocardial) pattern

— Pericardial enhancement supports myopericarditis

— Best performed within 2–3 weeks of symptom onset for highest yield

— In patients with chest pain and ACS-like presentation, rule out obstructive CAD — coronary angiography or coronary CTA depending on age/risk

— Especially required for >40 yo, multiple cardiac risk factors, or regional wall motion abnormalities

— Class I indications (AHA/ACC/ESC): unexplained new HF <2 weeks with hemodynamic compromise; or 2 weeks–3 months with dilated LV + new arrhythmia/AV block or failure to respond to standard therapy in 1–2 weeks

— Critical when giant cell, eosinophilic, or sarcoid myocarditis is suspected — because they require immunosuppression

— Dallas criteria: inflammatory infiltrate with myocyte necrosis

— Yield is improved with CMR-guided biopsy targeting LGE areas

Key distinction: LGE in myocarditis is mid-wall or subepicardial, sparing the subendocardium — opposite of MI, where injury starts subendocardially and progresses outward. This single CMR finding can clinch the diagnosis without biopsy in most viral lymphocytic cases.

Cardiac MRI (CMR) — non-invasive gold standard for diagnosis:

Coronary evaluation:

Endomyocardial biopsy (EMB) — definitive but selective:

PET/CT: if cardiac sarcoidosis suspected (FDG uptake with perfusion defects)

Genetic testing: in arrhythmogenic or familial-appearing cases to identify desmosomal mutations (overlap with arrhythmogenic cardiomyopathy)

Holter/event monitor: post-discharge to capture arrhythmia burden

Risk Stratification and First-Line Management Logic

— Stable, preserved EF, normal vitals: admit to telemetry, observation, supportive care

— HF with reduced EF, no shock: admit to step-down/telemetry, initiate GDMT cautiously

— Cardiogenic shock, arrhythmia, high-grade AV block, fulminant: ICU, vasoactive support, consider mechanical circulatory support and transfer to advanced HF center

— Most cases (viral/idiopathic lymphocytic): supportive care only — no proven benefit of antivirals or immunosuppression

— Giant cell: cyclosporine + steroids ± azathioprine; transplant evaluation

— Eosinophilic: high-dose steroids, remove offending drug

— Cardiac sarcoidosis: corticosteroids ± steroid-sparing agents

— ICI myocarditis: stop ICI, IV methylprednisolone 1 g/day; add MMF/infliximab if refractory

— Lyme carditis: IV ceftriaxone (or oral doxycycline if mild, no high-grade block)

— Bacterial: targeted antibiotics

— All patients: abstain from competitive and vigorous exercise for 3–6 months, until normalization of EF, biomarkers, and absence of arrhythmias on monitoring (AHA/ACC and Bethesda guidance)

— LVEF <40%, NYHA III–IV, syncope, sustained VT, complete heart block, RV dysfunction, biopsy-proven giant cell

— Troponin failing to downtrend, persistent LGE on follow-up CMR

Step 3 management: For a stable patient with chest-pain phenotype myocarditis and EF >50%, the entire inpatient management may consist of telemetry, serial troponin, NSAID/colchicine for pericardial component, follow-up CMR, and exercise restriction counseling — no need for HF medications if there's no LV dysfunction.

Step 1 — Triage by hemodynamic status:

Step 2 — Identify cause-specific therapies:

Step 3 — Activity restriction:

Adverse prognostic features:

Pharmacotherapy — First-Line Regimens

— ACEi or ARB (e.g., lisinopril, losartan) — or ARNI (sacubitril/valsartan) if hemodynamically tolerated

— Evidence-based beta-blocker: carvedilol, metoprolol succinate, or bisoprolol — hold if shock or high-grade AV block

— Mineralocorticoid receptor antagonist: spironolactone or eplerenone if EF ≤35% and K <5.0, eGFR >30

— SGLT2 inhibitor: dapagliflozin or empagliflozin — now standard regardless of diabetes

— Loop diuretic: furosemide IV for congestion; transition to PO when stable

— Indicated if LV thrombus seen on echo/CMR, AF, or severely depressed EF with low flow — typically warfarin or DOAC

— Amiodarone for sustained VT; avoid agents that prolong QT in setting of inflammation

— Temporary transvenous pacing for symptomatic high-grade AV block (often reversible in Lyme/viral)

— NSAIDs (ibuprofen or indomethacin) + colchicine for pericardial symptoms — but use cautiously with overt HF (NSAIDs worsen renal function and fluid retention)

— Consider aspirin-based regimen if NSAIDs contraindicated

— No routine immunosuppression for viral/lymphocytic myocarditis (no mortality benefit)

— Avoid digoxin in acute inflammation (proarrhythmic in inflamed myocardium per animal/clinical data; use only if needed for rate control)

— Avoid high-dose corticosteroids unless cause-specific indication

Board pearl: For ICI myocarditis, the answer is always discontinue ICI + IV pulse methylprednisolone 500–1000 mg daily, then taper. Mortality drops dramatically with early steroids. Do not wait for biopsy.

Heart failure with reduced EF — initiate guideline-directed medical therapy (GDMT) once euvolemic and stable BP:

Anticoagulation:

Arrhythmia management:

Myopericarditis component:

What NOT to use:

Procedures and Advanced Therapies

— IABP (intra-aortic balloon pump): modest support; less commonly used as first-line now

— Impella (axial flow pump): unloads LV, augments cardiac output up to 5.5 L/min

— VA-ECMO: preferred in biventricular failure or refractory VT/cardiac arrest; bridge to recovery or transplant

— Early MCS is critical in fulminant myocarditis because myocardial recovery is the rule if patient survives the acute event (>60–80% recovery rates)

— No ICD placement during the acute inflammatory window (first 3–6 months) unless sustained, hemodynamically significant VT/VF after reasonable recovery

— Use wearable cardioverter-defibrillator (LifeVest) as bridge during recovery period if EF remains <35%

— Reassess EF at 3 and 6 months; if EF persistently ≤35% on optimal GDMT → ICD candidacy

— Temporary transvenous pacing for transient AV block

— Permanent pacemaker only if AV block persists beyond 1–2 weeks despite antibiotics (Lyme) or recovery, or in sarcoid/giant cell

— Considered in giant cell myocarditis, refractory chronic HF, or those who cannot wean from MCS

— Giant cell has 50% recurrence post-transplant but still better survival than medical therapy

CCS pearl: When a young patient with fulminant myocarditis crashes despite dobutamine + norepinephrine, call CT surgery and the advanced HF service for VA-ECMO before further deterioration — outcomes are time-sensitive, and full myocardial recovery is achievable.

Temporary mechanical circulatory support (MCS) — for cardiogenic shock refractory to inotropes:

Permanent device decisions — defer in acute phase:

Pacemaker:

Pericardiocentesis: if tamponade physiology develops (rare in pure myocarditis, more in myopericarditis)

Cardiac transplantation:

Endomyocardial biopsy: procedurally done via right internal jugular access; risks include perforation, tamponade, arrhythmia

Special Populations — Elderly and Renal/Hepatic Impairment

— Less likely to present with classic prodrome; more often subtle dyspnea, fatigue, AF

— Higher mortality with myocarditis due to comorbid CAD, lower physiologic reserve

— Diagnostic challenge: must distinguish from ischemic cardiomyopathy — low threshold for coronary angiography

— Polypharmacy: review for drug-induced myocarditis (clozapine, mesalamine, sulfonamides, anticonvulsants, hydralazine)

— Initiate GDMT at lower starting doses, titrate slowly; watch for orthostatic hypotension

— Troponin elevation is common at baseline in CKD — trend the delta, not the absolute value

— Avoid NSAIDs entirely if eGFR <30 (worsens AKI, hyperkalemia)

— ACEi/ARB: continue if eGFR >30 and K <5.0; hold if AKI worsens >30% creatinine rise or K >5.5

— SGLT2 inhibitors: dapagliflozin approved down to eGFR 25, empagliflozin to eGFR 20 — continue for HF benefit

— Spironolactone: contraindicated if eGFR <30 or K >5.0

— Avoid gadolinium-based contrast for CMR if eGFR <30 (NSF risk with older agents; newer macrocyclic agents lower risk but use cautiously)

— Dose-adjust LMWH, antibiotics, and contrast for cath

— Congestive hepatopathy common in RV failure (cardiogenic cirrhosis pattern: elevated ALP, mildly elevated transaminases, elevated bilirubin)

— Shock liver pattern: AST/ALT in thousands, rapid resolution with hemodynamic recovery

— Avoid amiodarone if pre-existing liver disease (use alternative antiarrhythmic)

— Adjust colchicine dose; avoid in Child-Pugh C

— Anticoagulation: prefer warfarin over DOACs in advanced cirrhosis

Step 3 management: In an elderly patient with new HF and troponin elevation, do not stop at "viral myocarditis" — get coronary imaging. Missing concurrent ACS in the elderly is a common board pitfall and a real-world morbidity driver.

Elderly patients (>65):

Renal impairment (CKD or AKI):

Hepatic impairment:

Special Populations — Pregnancy, Pediatrics, Athletes

— Peripartum cardiomyopathy (PPCM): new HF with EF <45% from last month of pregnancy through 5 months postpartum — overlaps clinically with myocarditis; biopsy shows inflammation in subset

— Risk factors: multiparity, advanced maternal age, preeclampsia, African ancestry, multiple gestation

— Bromocriptine under investigation; mainstay is standard HF therapy

— Avoid teratogens during pregnancy: ACEi/ARB/ARNI (all trimesters — renal dysgenesis, oligohydramnios), spironolactone (antiandrogen), warfarin (1st trimester)

— Safe: hydralazine + nitrates, beta-blockers (labetalol, metoprolol), digoxin, loop diuretics (judicious)

— Postpartum: full GDMT, breastfeeding compatible with most agents except ARNI/spironolactone (use enalapril/captopril if needed during lactation)

— Future pregnancies: counsel against if EF does not normalize — high recurrence and mortality risk

— Viral etiology dominant (enteroviruses, adenovirus, parvovirus B19)

— Infants present nonspecifically: poor feeding, irritability, grunting, hepatomegaly — easily missed as sepsis or bronchiolitis

— Higher rate of progression to dilated cardiomyopathy

— IVIG sometimes used in pediatric myocarditis (data weak but practiced)

— Acute myocarditis is a leading cause of sudden cardiac death in young athletes

— Return-to-play guidance (AHA/ACC + Bethesda Conference + post-COVID consensus):

— Restrict from competitive sports for 3–6 months

— Before clearance: normalization of EF, troponin, ECG; absence of significant arrhythmia on exercise testing and ambulatory monitoring; ideally CMR resolution of edema (LGE can persist)

— mRNA vaccine-associated myocarditis in young males: typically mild, recovers with NSAIDs and rest; same return-to-play rules apply

Board pearl: A 22-year-old college soccer player with chest pain 5 days after COVID infection and a troponin of 0.8 should be benched for at least 3 months with CMR and exercise testing before return — clearance is an exam favorite.

Pregnancy and peripartum:

Pediatrics:

Athletes:

Complications and Adverse Outcomes

— Cardiogenic shock — leading early killer; requires inotropes and often MCS

— Malignant ventricular arrhythmias (sustained VT, VF) — cause of sudden cardiac death, especially in athletes; risk highest with active inflammation

— High-grade AV block — particularly in Lyme, sarcoid, giant cell, diphtheria; may require temporary pacing

— LV mural thrombus with embolic risk (stroke, mesenteric ischemia, limb ischemia) — anticoagulate when identified

— Pericardial effusion/tamponade in myopericarditis variants — monitor with serial echo

— Acute kidney injury from cardiorenal syndrome

— Congestive hepatopathy / shock liver

— Dilated cardiomyopathy (DCM): ~20–30% of viral myocarditis progresses to chronic DCM with persistent LV dysfunction

— Chronic heart failure with recurrent admissions

— Recurrent myocarditis (especially eosinophilic, sarcoid, giant cell)

— Inappropriate sinus tachycardia / POTS-like syndromes post-recovery

— Persistent LGE on CMR — independent predictor of arrhythmic events and mortality even if EF recovers

— Overall acute myocarditis: 5–10% in-hospital mortality

— Fulminant lymphocytic: high acute mortality but excellent recovery if survives (≥80% transplant-free survival at 10 years)

— Giant cell myocarditis: median survival without immunosuppression ~3 months; better with treatment + transplant

— ICI myocarditis: 25–50% mortality acutely

— Persistent EF <50%, persistent LGE, NYHA III–IV at presentation, biopsy-proven giant cell

— Failure of troponin to downtrend within 1–2 weeks

Key distinction: Fulminant lymphocytic myocarditis paradoxically has the best long-term prognosis if the patient survives the acute phase — the intense inflammation tends to resolve completely. Giant cell myocarditis, even when initially less dramatic, has the worst outcome without aggressive immunosuppression. Don't confuse acuity with prognosis.

Acute complications:

Subacute/chronic complications:

Mortality data:

Long-term prognostic markers:

When to Escalate Care — ICU, Consults, Inpatient Triage

— Hemodynamic instability: SBP <90, MAP <65, requirement for inotropes or vasopressors

— Cardiogenic shock with lactate >2, oliguria, cool extremities

— Sustained VT, VF, or high-grade AV block requiring pacing

— Acute respiratory failure from pulmonary edema requiring NIV or intubation

— Need for mechanical circulatory support (Impella, VA-ECMO)

— Severe LV dysfunction with EF <25% even if currently compensated (high deterioration risk)

— Hemodynamically stable HF with reduced EF

— Troponin still rising or arrhythmia monitoring needed

— IV diuresis without shock

— Chest pain phenotype with preserved EF, mild troponin elevation, no arrhythmia

— Cardiology (mandatory for all confirmed cases)

— Advanced HF / transplant cardiology for any shock, refractory HF, or suspected giant cell/sarcoid

— Cardio-oncology for ICI myocarditis

— Rheumatology for autoimmune/eosinophilic cases

— Infectious disease for Lyme, Chagas, HIV, suspected bacterial

— Electrophysiology for AV block or sustained VT

— Cardiac surgery for MCS or transplant evaluation

— Need for MCS beyond IABP

— Refractory shock or arrhythmia

— Biopsy required (some centers only)

— Transplant candidacy assessment

CCS pearl: On the CCS interface, in a hypotensive myocarditis patient, sequence the orders: ECG → IV access → ABG/lactate → bedside echo → call cardiology and ICU simultaneously → start dobutamine or norepinephrine based on BP → move location to ICU. Don't dawdle in the ED with serial bolus fluids.

ICU admission criteria:

Step-down/telemetry admission:

General ward / observation:

Consults — get early:

Transfer criteria — to a tertiary advanced HF/transplant center:

Disposition timing: Most stable myocarditis patients are observed 48–72 hours to confirm troponin downtrend and rhythm stability before discharge.

Key Differentials — Same-Category (Cardiac) Causes

— Shares troponin elevation, chest pain, ECG changes

— Key distinction: ACS shows regional wall motion abnormality matching coronary territory; obstructive CAD on cath. Myocarditis: patchy/diffuse, non-coronary distribution, mid-wall LGE

— Always rule out ACS in any patient with risk factors before settling on myocarditis

— Pleuritic positional chest pain, friction rub, diffuse ST elevation with PR depression

— Distinction from myopericarditis: pericarditis has normal troponin and normal LV function; myopericarditis has both pericardial inflammation and troponin rise

— Same NSAID/colchicine treatment but no exercise restriction needed in isolated pericarditis

— Postmenopausal woman with emotional/physical stressor, apical ballooning on echo

— Troponin mildly elevated, ECG with diffuse T-wave inversion and QT prolongation

— Clean coronaries; recovers within weeks

— Distinction: classic apical ballooning pattern, demographic, recent stressor; CMR shows edema without LGE

— Persistent uncontrolled tachyarrhythmia (e.g., AF with RVR for weeks)

— EF recovers with rate/rhythm control

— Pre-existing diagnosis; troponin usually only mildly elevated

— Young women, peripartum, fibromuscular dysplasia — angiography needed

— Subset of "myocarditis"; characterized by granulomas, conduction disease, VT — needs steroids

— Restrictive pattern, thickened walls on echo, low voltage ECG paradox — diagnosed with bone scintigraphy (PYP) or biopsy

Board pearl: The single most useful test to differentiate myocarditis from ischemic injury after a negative cath is cardiac MRI — mid-wall/subepicardial LGE essentially makes the diagnosis.

Acute coronary syndrome (STEMI/NSTEMI):

Acute pericarditis (without myocardial involvement):

Stress (Takotsubo) cardiomyopathy:

Tachycardia-induced cardiomyopathy:

Acute decompensated chronic HF (ischemic or non-ischemic DCM):

Spontaneous coronary artery dissection (SCAD):

Cardiac sarcoidosis:

Cardiac amyloidosis:

Key Differentials — Other-Category Causes

— Acute dyspnea, chest pain, troponin elevation (right heart strain), RV dysfunction on echo

— Distinction: D-dimer, CTPA, McConnell's sign (apical RV sparing), classic risk factors (immobilization, malignancy, OCPs)

— Source of infection, distributive shock features (warm, vasodilated initially), responds to antibiotics + fluids

— Stress-induced reversible LV dysfunction can mimic myocarditis but with clear infection source

— Especially viral pneumonia (influenza, COVID) — can coexist with myocarditis

— CXR/CT chest shows parenchymal disease

— Catecholamine surge → reversible cardiomyopathy with HTN crises, headaches, palpitations

— Plasma/urine metanephrines

— High-output HF, AF with RVR, tremor, hyperreflexia, fever

— TSH suppressed, free T4/T3 elevated

— Chest pain, troponin elevation, vasospasm, demand ischemia, or direct toxic cardiomyopathy

— Urine tox screen positive; avoid beta-blockers acutely (unopposed alpha-stimulation in cocaine)

— Cumulative dose history, gradual EF decline; usually not acutely inflammatory

— Troponin can rise from demand mismatch; treat underlying disorder

— Pulmonary edema with severely elevated BP; LV dysfunction reverses with BP control

— Tearing chest/back pain, pulse deficit, widened mediastinum — CT angiography mandatory before anticoagulation

Step 3 management: Always re-examine the troponin trajectory and clinical picture — many "myocarditis" presentations are actually type 2 MI (demand ischemia) from sepsis, anemia, or thyrotoxicosis. Treat the underlying driver and the troponin resolves without needing immunosuppression or biopsy.

Pulmonary embolism:

Sepsis / septic cardiomyopathy:

Pneumonia with cardiac strain:

Pheochromocytoma-induced cardiomyopathy:

Thyrotoxicosis (thyroid storm):

Cocaine/methamphetamine cardiotoxicity:

Anthracycline or trastuzumab cardiotoxicity:

DKA or other metabolic crises:

Hypertensive emergency:

Aortic dissection:

Secondary Prevention, Discharge Medications, Long-Term Plan

— ACEi/ARB or ARNI at maximally tolerated dose

— Beta-blocker (carvedilol, metoprolol succinate, or bisoprolol) — uptitrate every 2 weeks as tolerated

— MRA (spironolactone/eplerenone) if EF ≤35%, K <5, eGFR >30

— SGLT2 inhibitor (dapagliflozin or empagliflozin) regardless of diabetes status

— Loop diuretic at lowest dose for euvolemia

— Anticoagulation if LV thrombus (continue 3–6 months and reimage), AF, or prior embolic event

— NSAIDs + colchicine (3-month taper for colchicine) if myopericarditis component — discontinue NSAIDs once symptoms resolve

— Exercise restriction for 3–6 months until full recovery confirmed

— Gradual return to activity with cardiology clearance

— Avoid alcohol, cocaine, NSAIDs (long-term), nephrotoxins

— Sodium restriction (<2 g/day) and fluid restriction (<2 L/day) for symptomatic HF

— Daily weights, symptom diary

— Annual influenza vaccine (inactivated)

— Pneumococcal vaccines (PCV20 or PCV15+PPSV23)

— COVID-19 vaccination per current guidance — for post-mRNA vaccine myocarditis, consider non-mRNA platform or shared decision-making before further mRNA doses

— Discontinue offending drug permanently if drug-induced

— If ICI myocarditis: generally permanent discontinuation of ICI class

— If sustained VT or syncope occurred → typically 3–6 months no driving (varies by state DMV)

— Commercial drivers and pilots: stricter, require specialty clearance

Board pearl: SGLT2 inhibitors are now first-line GDMT for any HFrEF — including post-myocarditis — and should be on every discharge med list when EF is reduced, even without diabetes.

Discharge medication checklist (when LV dysfunction persists):

Activity and lifestyle counseling:

Vaccinations:

Avoid recurrence triggers:

Driving and occupational restrictions:

Follow-Up, Monitoring Parameters, Rehab and Counseling

— Cardiology clinic within 1–2 weeks post-discharge — repeat exam, vitals, weight, BMP, BNP

— Telephone or e-visit at 48–72 hours for medication tolerance

— Primary care within 7 days for medication reconciliation and care coordination

— Repeat TTE at 3 and 6 months to assess EF recovery

— Repeat CMR at 6 months to assess LGE resolution and edema clearance

— Holter or extended event monitor at 1–3 months to assess arrhythmia burden before clearing for exercise

— Repeat exercise stress test before return to competitive athletics

— Symptoms (NYHA class), weight, BP, HR, JVP, edema

— BMP for K, Cr (especially after ACEi/MRA titration)

— BNP/NT-proBNP trending

— Troponin if recurrent symptoms

— Med adherence and side effects (cough on ACEi, hyperkalemia on MRA, dizziness on beta-blocker)

— Refer once EF stable and no active arrhythmia — generally after 1–3 months

— Structured exercise plus risk-factor education improves outcomes

— Phase II cardiac rehab is covered by Medicare for HFrEF

— Recognize HF symptom worsening (weight gain >3 lb in 2 days, increased dyspnea, orthopnea)

— Avoid NSAIDs (worsen HF, AKI)

— Importance of medication adherence

— Sexual activity safe when patient can climb 2 flights of stairs without symptoms

— Pregnancy counseling for women of childbearing age — contraception while EF reduced

Step 3 management: The first post-discharge visit should always include medication reconciliation, symptom screening, BMP, and a discussion of exercise restriction timeline — this is a classic Step 3 ambulatory follow-up question stem.

Follow-up cadence:

Monitoring parameters per visit:

Cardiac rehabilitation:

Patient counseling content:

Psychosocial: screen for depression and anxiety at 4–6 weeks (PHQ-9, GAD-7) — high prevalence post-acute cardiac illness; SSRIs (sertraline) safe in HF

Ethical, Legal, and Patient Safety Considerations

— Endomyocardial biopsy consent must include risks of perforation (~0.5%), tamponade, arrhythmia, and right bundle branch block

— VA-ECMO and MCS require surrogate decision-maker discussions when patient is in shock and unable to consent — establish goals of care early, ideally with family meeting within 24–48 hours of ICU admission

— Fulminant myocarditis can deteriorate rapidly — early goals-of-care conversation with patient/family is a patient-safety imperative

— Address advance directives, code status, and acceptable level of intervention (e.g., would the patient accept transplant or LVAD?)

— Palliative care consult is appropriate even in potentially recoverable shock — for symptom management and family support

— Lyme carditis is reportable in most US states (state-dependent)

— Tuberculous pericarditis/myocarditis is reportable

— Vaccine-associated myocarditis should be reported to VAERS (Vaccine Adverse Event Reporting System) — this is the clinician's responsibility, not the patient's

— Discharge summary must explicitly list exercise restriction duration, follow-up timeline, and medication titration plan

— Reconcile medications — common error is failure to restart home meds or duplicate beta-blockers

— Ensure patient has access to medications (cost barriers with sacubitril/valsartan, SGLT2i — use patient assistance programs)

— Coaches/parents may pressure for early return; physician's documentation of restriction is legally protective and clinically appropriate — adhere to 3–6 month guidance

— Counsel on temporary driving restriction after syncope or VT; document discussion

— Provide FMLA documentation for prolonged recovery

— Occupational restrictions for commercial drivers, pilots, heavy machinery operators

Board pearl: Reporting a temporal association between mRNA COVID vaccine and myocarditis to VAERS is a required public health action, regardless of certainty of causation — it's how surveillance signals are generated. Failure to report is a recognized safety gap.

Informed consent for high-risk procedures:

Goals of care and palliative integration:

Mandatory reporting and public health:

Transitions of care safety:

Athlete return-to-play disputes:

Driving safety:

Disability and work clearance:

High-Yield Associations and Rapid-Fire Clinical Facts

Key distinction: Subendocardial LGE = ischemic injury; mid-wall/subepicardial LGE = myocarditis. Single most useful CMR teaching point for Step 3.

Most common cause (US): viral — parvovirus B19, HHV-6, coxsackie B, adenovirus, SARS-CoV-2

Lyme carditis: AV block in young person + tick exposure + erythema migrans → IV ceftriaxone (or PO doxycycline if mild block); pacing usually temporary

Chagas: Latin America, megacolon/megaesophagus, apical aneurysm, RBBB + LAFB

Giant cell myocarditis: young/middle-aged, refractory VT, thymoma/autoimmune association → cyclosporine + steroids, transplant

Eosinophilic myocarditis: peripheral eosinophilia, DRESS syndrome, recent new drug (sulfa, anticonvulsants) → withdraw drug + steroids

Cardiac sarcoidosis: AV block + VT + extracardiac sarcoid features; PET-FDG positive; treat with steroids ± methotrexate

ICI myocarditis: within 6 weeks of starting checkpoint inhibitor; often with myositis/myasthenia overlap → stop ICI, IV methylprednisolone 1g/day, infliximab if refractory

mRNA COVID vaccine myocarditis: young males 16–30, 2–4 days post-dose 2, mild, supportive care

Peripartum cardiomyopathy: last month pregnancy to 5 months postpartum; bromocriptine investigational; hydralazine/nitrates safe in pregnancy

Athletic SCD: myocarditis is a leading cause; restrict 3–6 months

Lake Louise CMR criteria: T2 (edema) + T1 (injury — LGE/native T1/ECV)

LGE pattern: mid-wall/subepicardial → myocarditis; subendocardial → ischemic

Fulminant myocarditis paradox: worst acute presentation, best long-term prognosis if survives

Worst prognosis: giant cell myocarditis

ECG findings: sinus tach (most common), diffuse ST elevation + PR depression, AV block, low voltage, QT prolongation

No benefit: routine immunosuppression in viral lymphocytic myocarditis

Always do: rule out ACS in any troponin-positive patient with risk factors

Avoid: NSAIDs in HF, beta-blockers in cocaine MI, digoxin in acute inflammation

Anticoagulate: LV thrombus, AF, severely depressed EF with stasis

GDMT for HFrEF post-myocarditis: ACEi/ARB/ARNI + beta-blocker + MRA + SGLT2i + diuretic PRN

Return-to-play: normalize EF, troponin, ECG; no arrhythmia on Holter/exercise test; 3–6 months minimum

Board Question Stem Patterns

— 22M, viral illness 10 days ago, now pleuritic chest pain, troponin 2.5, ECG diffuse ST elevation, clean coronaries

— Answer: cardiac MRI to confirm myocarditis; exercise restriction 3–6 months; NSAIDs + colchicine

— 65F on pembrolizumab 4 weeks, presents with dyspnea, troponin 1.8, mild LV dysfunction

— Answer: stop ICI, IV methylprednisolone 1 g/day, cardio-oncology consult

— 30M from Connecticut, recent tick bite, EM rash, now syncope, ECG shows complete heart block

— Answer: Lyme carditis → IV ceftriaxone, temporary pacing if symptomatic; PPM not indicated

— 35F with viral prodrome, now BP 80/50, lactate 4, EF 15%, sustained VT

— Answer: ICU, inotrope/pressor support, VA-ECMO consideration, transfer to transplant center

— 32F, 2 months postpartum, new dyspnea, EF 30%

— Answer: peripartum cardiomyopathy — hydralazine + nitrates + beta-blocker if breastfeeding; counsel against future pregnancies if EF doesn't recover

— 40M with progressive HF, sustained VT despite amiodarone, biopsy shows multinucleated giant cells

— Answer: giant cell myocarditis → cyclosporine + steroids + transplant evaluation

— Patient started on phenytoin 4 weeks ago, rash, eosinophilia 15%, troponin elevated

— Answer: DRESS/eosinophilic myocarditis → stop phenytoin, high-dose steroids

— Athlete recovering from myocarditis at 4 months, asymptomatic, EF 60%, no LGE — can he return?

— Answer: after Holter and exercise test demonstrating no arrhythmia and full recovery

— Recovering myocarditis patient with EF 30% — which medication is mandatory?

— Answer: full GDMT including SGLT2 inhibitor regardless of diabetes

— Think Lyme first if endemic; sarcoid/giant cell otherwise

Step 3 management: Pattern recognition is everything — match the demographic, exposure, ECG pattern, and biopsy clues to the etiology, then apply the cause-specific treatment.

Stem 1 — "Young athlete with chest pain after URI":

Stem 2 — "ICI patient with new fatigue and troponin":

Stem 3 — "Hiker with syncope":

Stem 4 — "Fulminant presentation":

Stem 5 — "Postpartum HF":

Stem 6 — "Refractory VT in young adult":

Stem 7 — "Eosinophilia plus new HF":

Stem 8 — "Return-to-play decision":

Stem 9 — "Discharge regimen":

Stem 10 — "ECG with new AV block in a febrile young adult":

One-Line Recap

Acute myocarditis is myocardial inflammation — most commonly viral and self-limited — that demands rapid hemodynamic triage, cause-specific therapy when an immunologic or treatable etiology is identified, GDMT for residual LV dysfunction, and a 3–6 month exercise restriction with structured cardiology follow-up.

Board pearl: When in doubt on the exam, the answer chain is: rule out ACS → get cardiac MRI → identify and treat the specific cause → start GDMT if EF reduced → restrict exercise 3–6 months → schedule structured follow-up. Master this sequence and you will get every myocarditis question right on Step 3.

Diagnose with: ECG + troponin + BNP + TTE first, then cardiac MRI (Lake Louise criteria); reserve endomyocardial biopsy for fulminant, unexplained, or suspected giant cell/eosinophilic/sarcoid disease

Treat by etiology: supportive care for viral/lymphocytic; IV steroids + stop drug for ICI and eosinophilic; cyclosporine + steroids + transplant eval for giant cell; ceftriaxone for Lyme; standard GDMT (ACEi/ARNI + beta-blocker + MRA + SGLT2i) for residual HFrEF

Escalate early: ICU + inotropes + VA-ECMO for fulminant shock — survival in fulminant disease yields excellent long-term recovery, so do not withhold MCS

Follow up rigorously: repeat TTE at 3 and 6 months, CMR at 6 months, Holter before exercise clearance, cardiac rehab referral, and exercise restriction for 3–6 months — and always report vaccine-associated cases to VAERS