In a 28-year-old man with known dilated cardiomyopathy and an ejection fraction of 30%, who now has globally dilated chambers, severe mitral regurgitation, moderate pulmonary arterial hypertension, and fever, what is the most likely cause?

Acute Rheumatic Fever with Rheumatic Carditis

In a 28-year-old man with known dilated cardiomyopathy who now presents with fever, severe mitral regurgitation, and moderate pulmonary hypertension, the most likely acute cause is infective endocarditis superimposed on his underlying cardiomyopathy, though acute rheumatic fever (particularly in endemic regions) or viral myocarditis causing acute decompensation must also be urgently considered.

Primary Diagnostic Considerations

Infective Endocarditis (Most Urgent to Exclude)

• Blood cultures must be obtained immediately before any antibiotic administration, as fever with new or worsening valvular regurgitation in a patient with structural heart disease is endocarditis until proven otherwise 1, 2
• Echocardiography should assess for vegetations, valve destruction, and intracardiac complications including abscess formation 1
• Look for peripheral stigmata including splinter hemorrhages, Osler nodes, Janeway lesions, and Roth spots on examination 2

Acute Rheumatic Fever

• Apply the Revised Jones Criteria: evidence of preceding group A streptococcal infection plus either 2 major manifestations OR 1 major plus 2 minor manifestations 2
• The presence of moderate-to-severe mitral regurgitation on echocardiography qualifies as carditis (a major criterion), which can be clinical and/or subclinical echocardiographic valvulitis 2
• Document preceding streptococcal infection through throat culture, rapid antigen test, or elevated/rising streptococcal antibody titers (ASO, anti-DNase B) 2
• Assess inflammatory markers including ESR and CRP as minor criteria 2
• Rheumatic heart disease remains a major cause of heart failure in young adults in Sub-Saharan Africa and low-income countries, accounting for up to 40% of heart failure cases in some populations 1

Viral Myocarditis with Acute Decompensation

• Coxsackievirus serotype B is a known cause of infectious myocarditis leading to dilated cardiomyopathy, with diagnosis based on clinical findings and elevated IgM antibodies to CV-B 3
• Fever with acute worsening of ventricular function and new mitral regurgitation may represent acute viral myocarditis superimposed on chronic DCM 3
• Up to one-third of dilated cardiomyopathy cases may have an inflammatory or concealed myocarditis etiology 1

Understanding the Severe Mitral Regurgitation

Secondary (Functional) Mitral Regurgitation Mechanisms

• In dilated cardiomyopathy, mitral regurgitation is typically secondary to ventricular dilation and dysfunction rather than primary valve pathology 1
• The dilated left ventricle causes papillary muscle displacement and annular dilation, preventing proper leaflet coaptation 4
• Severe mitral regurgitation creates a vicious cycle: regurgitant volume further dilates the left atrium and ventricle, worsening the regurgitation 4

Distinguishing Primary vs. Secondary Causes

• Critical distinction: Primary mitral regurgitation (intrinsic valve pathology from endocarditis or rheumatic disease) versus secondary functional regurgitation from ventricular dilation fundamentally changes management 4
• Assess jet direction on echocardiography: laterally and posteriorly directed jets suggest functional MR from SAM, while anteriorly directed jets suggest intrinsic valve abnormality 1
• Look for vegetations, leaflet destruction, flail segments, or rheumatic valve thickening to identify primary valve pathology 1, 2

Pulmonary Hypertension Context

• Moderate pulmonary arterial hypertension develops from chronic elevation of left atrial pressure transmitted backward from the failing left ventricle and severe mitral regurgitation 1
• The combination of severe MR with moderate PAH indicates chronicity but can acutely worsen with superimposed infection or inflammatory process 1

Diagnostic Algorithm

Immediate Actions (Within Hours)

1. Obtain 3 sets of blood cultures from different sites before antibiotics 2
2. Perform comprehensive echocardiography assessing for vegetations, valve destruction, ventricular function, and intracardiac thrombi 1, 5
3. Check inflammatory markers (ESR, CRP, CBC with differential) 2
4. Obtain streptococcal serology (ASO, anti-DNase B) 2
5. Check viral serologies including Coxsackievirus IgM if available 3

Clinical Examination Focus

• Search meticulously for peripheral stigmata of endocarditis 2
• Assess for other Jones criteria: polyarthritis (migratory large joint involvement), erythema marginatum, subcutaneous nodules, chorea 2
• Evaluate for signs of acute decompensated heart failure: pulmonary rales, elevated JVP, peripheral edema, S3 gallop 1

Risk Stratification

• Patients with dilated cardiomyopathy have increased risk for intracardiac thrombi (up to 60% at autopsy), which can embolize causing MI from coronary emboli 1, 6
• Assess for LV thrombus on echocardiography, as this carries embolic risk and influences anticoagulation decisions 1

Critical Pitfalls to Avoid

• Never dismiss endocarditis based on negative initial blood cultures—obtain multiple sets and consider culture-negative endocarditis if clinical suspicion remains high 2
• Do not confuse physiological mitral regurgitation with pathological—use strict Doppler criteria and assess leaflet morphology for structural abnormalities 1
• Do not delay empiric antibiotic therapy if endocarditis is strongly suspected after blood cultures are obtained, as mortality increases with treatment delay 2
• Do not assume all mitral regurgitation is functional—actively search for primary valve pathology that may require different management 4
• In endemic regions, do not dismiss acute rheumatic fever based solely on age, as it remains prevalent in young adults in resource-limited settings 1, 2

Geographic and Epidemiologic Context

• Rheumatic heart disease prevalence varies dramatically by region: extremely high in Sub-Saharan Africa (up to 40% of HF cases) versus <1 per 100,000 in industrialized countries 1
• Consider the patient's geographic origin and recent travel when weighing likelihood of rheumatic fever versus other etiologies 1
• Ischemic heart disease accounts for only 15% of heart failure in Africa compared to 60% in Eastern Europe and Middle East, making non-ischemic causes more likely in young African patients 1