In an adult, what does a point of maximal impulse located in the sixth intercostal space at the mid‑clavicular line indicate, and what initial investigations and management are recommended?

Point of Maximal Impulse at the 6th Intercostal Space

A point of maximal impulse (PMI) located at the 6th intercostal space at the mid-clavicular line indicates left ventricular enlargement and requires immediate echocardiographic evaluation to assess for dilated cardiomyopathy, left ventricular hypertrophy, or other structural cardiac pathology. 1

Clinical Significance

Lateral and inferior displacement of the apical impulse beyond the normal 5th intercostal space inside the mid-clavicular line strongly suggests left ventricular enlargement. 1 The American College of Cardiology states that lateral displacement of the apical impulse beyond the mid-clavicular line is a key physical finding for left ventricular enlargement. 1

Differential Diagnosis

The 6th intercostal space location indicates one of several pathological conditions:

• Dilated cardiomyopathy is a primary consideration when the PMI is displaced laterally and inferiorly, as reported by the European Society of Cardiology. 1

• Left ventricular hypertrophy from chronic pressure overload (hypertension, aortic stenosis) causes displacement of the apical impulse, according to the American Heart Association. 1

• Chronic volume overload states including severe mitral regurgitation or aortic regurgitation can produce this finding. 1

• In hypertrophic cardiomyopathy, a prominent point of maximal impulse is typically present, shifted laterally and either bifid or trifid, with the PMI often displaced. 2

Initial Investigations

Physical Examination Details

Beyond PMI location, assess these specific findings:

• Measure the diameter of the apical impulse: A diameter ≥4.0 cm is 96% sensitive and 96% specific for left ventricular dilatation. 3

• Assess the quality of the impulse: A sustained apical impulse indicates pressure overload (aortic stenosis, hypertension), while a hyperdynamic impulse suggests volume overload or high-output states. 1

• Evaluate for parasternal heave/lift, which suggests right ventricular hypertrophy or enlargement. 1

• Auscultate for a fourth heart sound (S4), which indicates a noncompliant left ventricle and is commonly present in hypertrophic cardiomyopathy. 2

• Perform provocative maneuvers (Valsalva, standing from squatting) to assess for dynamic left ventricular outflow tract obstruction if hypertrophic cardiomyopathy is suspected. 2

Diagnostic Testing Algorithm

1. Transthoracic Echocardiography (First-Line, Mandatory)

• Echocardiography is recommended as the initial evaluation in all patients with suspected cardiac enlargement based on PMI displacement. 2

• Assess left ventricular dimensions, wall thickness, systolic function (ejection fraction), and diastolic function. 2

• Evaluate for regional wall motion abnormalities suggesting prior myocardial infarction. 2

• Measure left ventricular outflow tract gradient at rest and with provocative maneuvers if hypertrophic cardiomyopathy is suspected. 2

• Assess mitral valve anatomy and function, particularly for mitral regurgitation. 2

2. 12-Lead Electrocardiogram

• Obtain to assess for left ventricular hypertrophy voltage criteria, pathological Q waves, or conduction abnormalities. 2

• Ensure proper lead placement: V4 should be at the 5th intercostal space in the midclavicular line, with V5 and V6 at the horizontal plane of V4. 2

• Inferior placement of V5 and V6 in the 6th intercostal space or lower can alter amplitudes used in diagnosing ventricular hypertrophy and should be avoided. 2

3. Additional Testing Based on Echocardiographic Findings

• Cardiac biomarkers (troponin, BNP/NT-proBNP) if acute decompensation or ischemia is suspected. 2

• Cardiac MRI for tissue characterization if infiltrative disease (amyloidosis, sarcoidosis) or myocarditis is suspected based on echocardiographic findings. 2

• Coronary angiography if ischemic cardiomyopathy is the suspected etiology. 2

• Genetic testing if hypertrophic cardiomyopathy or familial dilated cardiomyopathy is diagnosed. 2

Common Pitfalls to Avoid

• Do not dismiss PMI displacement as a normal variant: Research demonstrates that in the full left lateral position, the lateral margin of the apex beat in healthy adults is located in a 3-cm-wide area from the left anterior axillary line towards the mid-clavicular line, not beyond it. 3

• Obesity, emphysema, or thick chest walls may obscure the apical impulse even when cardiac enlargement is present, so absence of a palpable PMI does not exclude cardiomegaly. 1

• Avoid confusing ECG lead misplacement with actual cardiac pathology: Inferior placement of precordial leads can simulate or mask ventricular hypertrophy. 2

Management Priorities

The management strategy depends entirely on the underlying etiology identified by echocardiography, but initial steps include:

• Assess volume status and optimize diuretic therapy if heart failure with volume overload is present. 2

• Initiate guideline-directed medical therapy for heart failure with reduced ejection fraction if dilated cardiomyopathy is confirmed. 2

• Control hypertension aggressively if left ventricular hypertrophy from pressure overload is identified. 2

• Refer to cardiology for consideration of septal reduction therapy (surgical myectomy or alcohol septal ablation) if symptomatic hypertrophic cardiomyopathy with outflow tract obstruction is diagnosed. 2

• Evaluate for implantable cardioverter-defibrillator if left ventricular systolic dysfunction is severe or if hypertrophic cardiomyopathy with high-risk features for sudden cardiac death is present. 2