Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (51 page)

   It is important to recognize that HF includes symptoms not only from systolic dysfunction but from HF with preserved ejection fraction (HFpEF), which is predominant in the elderly.

   At 40 years of age, the lifetime risk of CHF in both men and women is 1 in 5 (without MI, it is 1 in 9 for men and 1 in 6 for women).

   In developed countries, CAD accounts for 60–75% of symptomatic cases of HF and has surpassed hypertension as an etiologic factor in HF (although hypertension continues to have a higher attributable risk in the general population due to its prevalence).

   Both the prevalence and incidence of CHF increase with age, roughly doubling with each decade of life to >50% in individuals over 70 years of age. Women are more likely than men to have CHF with preserved systolic function.

   Who Should Be Suspected?

   History alone is insufficient to make a diagnosis of HF given the nonspecific presenting symptoms. Chronic HF is more likely to present with anorexia and fatigue with decreased prevalence of rales on exam (sensitivity of 15%) due to increases in pulmonary vascular resistance and capacitance.

   However, history (particularly functional limitation) is essential for assessing HF severity, which is critical for prognosis, staging, and appropriateness of advanced treatment options.

   Dyspnea has high sensitivity for HF (87%) but low specificity (51%). Signs of right-sided congestion are the most sensitive exam findings for HF with JVP of >12 mm Hg and hepatojugular reflux at 65% and 85%, respectively. A finding of a displaced apical impulse on exam in patients with dyspnea has the best combination of sensitivity, specificity, and predictive value for systolic HF.

   Large registries have identified the following risk factors as having the largest population attributable risk for heart failure: CAD, cigarette smoking, hypertension, obesity, diabetes, and valvular heart disease.

   Special consideration should be given to individuals with a familial history of cardiomyopathy. A detailed history dating back three generations should be obtained to determine age of onset, inheritance pattern, and lethality along with possible nongenetic risk factors. As upward of 30 cardiomyopathy genes have been identified, current guidelines recommend referral to genetic counseling whenever appropriate. Testing (and screening frequency) of the proband and family members will be determined by the type of cardiomyopathy. Mode of inheritance is usually dominant with antibodies present in 30% of patients and first-degree relatives. Common screening measures of relatives include echocardiography, treadmill testing, Holter monitor (hypertrophic), and/or cardiac MRI in addition to disease-specific genetic testing.

   Diagnostic and Laboratory Findings

   
Electrocardiogram
: A normal ECG has a 98% negative predictive value for systolic dysfunction. Dilated cardiomyopathy (DCM) often presents with conduction abnormality (first-degree AV block, LBBB, fascicular block, or nonspecific QRS widening). Low limb lead voltage with loss of precordial R waves suggests infiltrative cardiomyopathies (amyloidosis) and with LVH suggests idiopathic dilated cardiomyopathy.