Accentuated Second Heart Sound: Clinical Significance and Evaluation
An accentuated (loud) second heart sound, particularly the pulmonary component (P2), is a key physical finding indicating elevated pulmonary artery pressure and should prompt immediate evaluation for pulmonary hypertension. 1
What It Indicates
An accentuated P2 audible at the apex occurs in 90% of patients with idiopathic pulmonary arterial hypertension (IPAH), reflecting increased force of pulmonary valve closure due to elevated pulmonary artery pressure 1. This finding represents one of the most sensitive physical examination signs for pulmonary hypertension (PH), though it can be subtle and is often overlooked in early disease 2.
Other Causes to Consider:
- Anemia: Lower blood viscosity reduces damping forces on semilunar valves, causing accentuated sounds across both aortic and pulmonary components 3
- Congenitally corrected transposition: Anterior position of the aortic valve produces a loud S2, making it difficult to distinguish from pulmonary hypertension 4
Important Caveat:
While P2 hyperphonesis is traditionally considered valuable for PH diagnosis, recent evidence shows low sensitivity (60%) and specificity (22%) when rigorously tested against echocardiographic parameters in interstitial lung disease patients 5. This means the finding should trigger further workup but cannot rule in or out PH definitively.
How to Evaluate
Initial Assessment:
Look for accompanying signs of pulmonary hypertension 2, 1:
- Left parasternal lift (RV hypertrophy)
- Early systolic ejection click
- Midsystolic ejection murmur
- RV S4 gallop (38% of cases)
- Prominent jugular "a" wave
Signs of advanced disease/RV failure 2, 1:
- Holosystolic murmur of tricuspid regurgitation (increases with inspiration)
- RV S3 gallop (23% of cases)
- Elevated jugular venous pressure with V waves
- Hepatojugular reflux and pulsatile liver
- Peripheral edema (32% of cases)
- Ascites
- Cool extremities with diminished pulse pressure (ominous finding indicating severely reduced cardiac output)
Diagnostic Workup Algorithm:
- Right axis deviation
- RV hypertrophy (55% sensitivity, 70% specificity)
- RV strain pattern (more sensitive than hypertrophy)
- QRS and QTc prolongation suggest severe disease
- P pulmonale
Chest radiograph 2:
- Central pulmonary arterial dilatation with peripheral "pruning"
- RA and RV enlargement
- Abnormal in 90% of IPAH patients at diagnosis
Echocardiography (definitive non-invasive test):
- Assess pulmonary artery systolic pressure
- Evaluate RV function and size
- Identify structural abnormalities
Right heart catheterization 2:
- Gold standard for confirming PH diagnosis
- Mean PAP ≥25 mmHg defines PH
- Distinguishes pre-capillary from post-capillary PH
Search for Underlying Etiology 1:
- Family history: Genetic PAH, connective tissue disease
- Toxic exposures: Appetite suppressants, chemotherapy agents
- HIV status
- Thromboembolic history: Even without prior DVT/PE, evaluate for chronic thromboembolic PH
- Physical findings suggesting cause:
- Telangiectasia, sclerodactyly → scleroderma
- Inspiratory crackles → interstitial lung disease
- Spider nevi, palmar erythema → liver disease
- Digital clubbing → consider PVOD, cyanotic CHD, or lung disease (rare in IPAH)
Management Approach
The presence of an accentuated P2 with supporting clinical findings mandates referral to a PH specialist for comprehensive evaluation 2. Early detection is critical as symptoms are non-specific (dyspnea, fatigue, weakness, syncope) and initially only occur with exertion, progressing to rest symptoms only in advanced cases 2.
Common Pitfalls:
- Do not dismiss a normal ECG: It does not exclude PH, especially in mild disease 2
- Do not rely on P2 accentuation alone: The finding has limited specificity and requires corroborating evidence 5
- Do not overlook anemia: Check hemoglobin before attributing loud S2 solely to PH 3
- Recognize atrial arrhythmias: Atrial flutter/fibrillation occur in 25% of PH patients after 5 years and cause clinical deterioration requiring prompt management 2