Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (56 page)

   HF presentation in a younger patient with preserved EF suggests etiology other than diastolic HF.

   If clinical signs of severe venous congestion are present (ascites, hepatomegaly) out of proportion to left-sided symptoms, infiltrative CM, pulmonary hypertension, or constrictive pericarditis should be considered.

   Early systolic flow murmurs and bounding pulses suggest high output failure and a venous hum or thrill an AV fistula or malformation as etiology of HF.

   Amyloid should be considered with low ECG voltage and LV hypertrophy on echocardiogram.

   Dynamic outflow tract murmur along with ECG hypertrophy without history of hypertension accompanies both aortic stenosis and hypertrophic cardiomyopathy. Echocardiography will aid in the differentiation of both conditions.

   Diagnostic and Laboratory Findings

   Core laboratory: similar to HF with reduced EF. CBC, renal function, liver, and thyroid serologies to rule out confounding clinical syndromes.

   
BNP and NT-proBNP
: Should be measured early if the diagnosis of HF is uncertain. Both are elevated in diastolic HF. There is no threshold to differentiate systolic from diastolic HF, but BNP and NT-proBNP tend to be higher in HF with LV dysfunction. Acute HF diagnostic thresholds are BNP >100 pg/mL and NT-proBNP >300 pg/mL and are independent predictors of adverse events.

   If troponin is >99th percentile upon presentation, etiologies of coronary disease, infiltrative cardiomyopathy (amyloid), and myocarditis should be considered.

   
Echocardiography
: HFpEF is defined as EF ≥ 50%. Patients with mildly reduced EF (40–49%) should be evaluated and treated as HF with reduced EF (see Congestive Heart Failure above). Differential diagnosis of HFpEF can be performed with echocardiography, differentiating between CAD (regional wall motion abnormalities), amyloid/infiltrative disease, hypertrophic CM, constrictive pericarditis, and mitral/aortic regurgitation. Doppler criteria including mitral inflow, pulmonary venous velocity, and mitral annular motion by tissue Doppler can effectively diagnose presence of abnormal diastolic function.

   
Hypertrophic cardiomyopathy (HCM)
: Diagnosed by unexplained increase in LV wall thickness (13–60 mm) with a nondilated LV chamber. Obstruction of the LV outflow track or systolic anterior motion of the mitral valve with concomitant mitral regurgitation may or may not be present. HCM is the most common genetic cardiomyopathy (1:500) with diverse clinical presentation and course. Echocardiography or CMR may be used for diagnosis. LV wall thickness may be noncontiguous. Commercially available genetic testing may be performed to confirm diagnosis (not prognostic) but should be performed in at-risk relatives to help define screening frequency (echo) and participation in competitive sports (ACC/ESC recommended). Extreme LV hypertrophy on imaging (≥30 mm), nonsustained ventricular tachycardia on ECG, and failure to augment blood pressure with exercise increase the risk of sudden cardiac death and warrant consideration of ICD.