The most appropriate diagnostic test to perform next in this patient is myocardial perfusion imaging stress testing. This patient has evidence of new-onset heart failure as evidenced by her clinical presentation (decreased exercise tolerance, jugular venous distention, crackles on lung examination, and lower extremity edema). A diagnosis of new-onset heart failure should be confirmed by echocardiography, which has both high sensitivity and specificity for heart failure and may be useful in evaluating for specific possible causes of heart failure, such as valve dysfunction. Treatable causes of heart failure include coronary artery disease (CAD), thyroid disease, alcohol abuse, and some valvular diseases (such as aortic stenosis, if repaired early) and should be looked for during the initial evaluation.

As many as two thirds of cases of heart failure are caused by CAD. This patient has several risk factors for cardiovascular disease, including hypertension and a history of smoking. Her electrocardiogram (ECG) demonstrates left bundle branch block and her echocardiogram demonstrates an akinetic left wall, both of which suggest CAD. Patients with heart failure and multiple risk factors or symptoms of CAD should be evaluated by either a stress test or cardiac catheterization. The reason to evaluate for CAD is that revascularization by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery may improve her left ventricular ejection fraction and reduce her symptoms of heart failure. Noninvasive exercise testing is often performed initially to provide information about the possible presence of ischemic heart disease but also to assist in risk stratification and prognosis. Cardiac catheterization may be helpful in patients with suggestive findings on noninvasive testing or may be an appropriate initial study in selected patients.

Cardiac magnetic resonance (CMR) imaging is not part of the routine evaluation of new-onset heart failure but may be used if an infiltrative or an inflammatory process is suspected, such as myocarditis, hemochromatosis, Wilson disease, or sarcoidosis. If the patient's evaluation for CAD as a cause of her heart failure is normal and myocarditis is a consideration, CMR imaging may be a reasonable test.

Coronary artery calcium scoring is a method of measuring vascular calcification in the coronary arteries, with increased levels of calcium being associated with an increased burden of atherosclerotic plaque and cardiac events. Its optimal use may be in providing additional information for making therapeutic decisions in asymptomatic patients at intermediate risk for atherosclerotic cardiovascular disease. However, its role in evaluating patients with heart failure believed to be caused by CAD has not been established.

Endomyocardial biopsy is indicated in patients with heart failure that progresses despite medical therapy and those with malignant arrhythmias to evaluate for giant cell myocarditis, as well as in those in whom amyloidosis or hemochromatosis is suspected. Endomyocardial biopsy is not indicated in this patient with evidence of heart failure in whom CAD has not been evaluated.