Heart Failure and Ischemia
For a patient who is admitted to the hospital for heart failure, hospitalists provide patient care at each step of the patient’s stay, including monitoring his or her condition, adjusting medications, and providing care before and after diagnostic or therapeutic procedures, such as angiography or device implantation. Because the etiology and progression of heart failure are different for each patient, the assessment and treatment pathways, as well as the role of the hospitalist in providing care, might also be different for each patient.
Patients hospitalized with heart failure might have underlying coronary ischemia.1 The risk of cardiac events in patients with heart failure and ischemia, as well as the most effective treatment options to lower their risk, is different from that for patients with heart failure but no ischemia.1 Therefore, it is important to determine the etiology of heart failure in all patients prior to making decisions on a course of treatment.1 In addition to detecting myocardial ischemia and viability, gated myocardial perfusion imaging (MPI) can provide information about left ventricular (LV) function that can be used to refine risk assessment and inform management decisions, most notably electrophysiology like an automated implantable cardioverter-defibrillator (AICD) or cardiac resynchronization therapy (CRT). In this article, we will discuss the definition of ischemic and nonischemic heart failure, the ways in which to diagnose the presence of ischemia in these patients, and options for patient care.
ISCHEMIC VS NONISCHEMIC HEART FAILURE
In patients with suspected heart failure, it is important to determine the etiology of the disease in order to determine a course of management. Patients with heart failure for which the cause is unknown are referred to as having nonischemic, dilated, or idiopathic cardiomyopathy.2 Nonischemic cardiomyopathy is not related to underlying coronary artery disease (CAD), and might be due to congenital heart defects, valvular disease, severe hypertension, or other causes.2 Studies suggest that the mechanism of sudden death may differ between ischemic and nonischemic heart failure patients, further emphasizing the importance of differentiating between etiologies.1
DETECTION OF ISCHEMIA
Determining whether LV dysfunction in heart failure is due predominantly to the consequences of CAD (ie, ischemic cardiomyopathy), or to nonischemic cardiomyopathy, is a critical early step in the management of heart failure patients.4 Initial assignment of HF etiology should be as specific as possible. Significant differences in prognosis are commonly noted among the various etiologies of HF, and identification of specific etiologies might trigger specific directions for evaluation and treatment.1 Current guidelines recommend that patients with heart failure and symptoms suggestive of ischemia should undergo coronary catheterization to assess the need for revascularization.1,3 Gated radionuclide myocardial perfusion imaging (MPI) with either single photon emission computed tomography (SPECT) or positron emission tomography (PET) is commonly used to assess myocardial viability and ischemia in patients with heart failure and suspected CAD.4 Although the presence of any perfusion abnormality on MPI is not highly specific for CAD, the pattern of perfusion abnormalities might assist in the differentiation between an ischemic and nonischemic etiology of heart failure.4 Clear ischemic etiology might ultimately result in catheterization. Once the etiology of heart failure is established with a diagnosis of CAD, clinicians will be better equipped to make decisions about treatment.
MANAGEMENT OF ISCHEMIC AND NONISCHEMIC CARDIOMYOPATHY
As with all patients with CAD, current guidelines recommend that known cardiac risk factors should be managed medically in patients with ischemic cardiomyopathy in order to reduce the risk of events. These factors include hyperlipidemia (optimized to NCEP ATP III recommended levels),5 smoking, metabolic syndrome, physical inactivity, overweight or obesity, and hypertension.1 The results of noninvasive testing can help determine whether patients with ischemic cardiomyopathy are candidates for revascularization.1,4 Revascularization could be required in patients with heart failure and occlusive CAD to relieve chest pain or other ischemia-related symptoms.1 Revascularization could also be appropriate in patients with heart failure who have viable myocardium in the areas of obstructive CAD or inducible ischemia in order to recover blood flow and LV function.1
The management of heart failure in patients with either nonischemic or ischemic cardiomyopathy is dependent on a number of factors, including the etiology, the presence of arrhythmias or conduction abnormalities, the level of LV dysfunction (as measured by LVEF), and the degree of hypertension, among many others.1 A brief summary of the assessment and management pathways for patients with ischemic or nonischemic cardiomyopathy, based on current guidelines, is shown in Figure 1. Please note that, for new heart failure patients who are being considered for AICD or CRT due to left ventricular (LV) dysfunction, LV function should be reassessed after three to six months of optimal medical therapy.1
Determining the etiology of heart failure—ischemic or nonischemic—will help determine the best method for evaluation and will impact treatment decisions. Patients who are hospitalized with heart failure and who have either asymptomatic ischemic cardiomyopathy or non-ischemic cardiomyopathy might be candidates for noninvasive imaging to detect the extent of underlying CAD. These imaging results, in turn, can help identify patients for whom revascularization might alleviate chest pain symptoms or improve LV dysfunction.
Matthew Landler, MD, from the Northwestern University Feinberg School of Medicine, is the consultant for The Heart and Hospital Medicine series. Dr. Landler is a consultant for Astellas Pharma US, Inc.