Direct assessment of diastolic function unnecessary
Evidence of diastolic dysfunction as determined by echocardiography or cardiac catheterization has been debated as a necessary third diagnostic criterion.24 The problem, though, is that there is no simple means of reliably diagnosing diastolic dysfunction with echocardiography (E:A ratios, deceleration or relaxation times), and that performing cardiac catheterization to measure LVEDP is impractical.22
Furthermore, Zile et al have shown that, though cardiac catheterization helps to confirm diastolic dysfunction, it is not necessary to establish the diagnosis. In this study, 63 patients with clinically defined diastolic heart failure based on the Framingham criteria underwent diagnostic cardiac catheterization; 58 (92%) of these patients were also found to have an abnormal LVEDP, indicative of diastolic dysfunction.25 Therefore, the diagnosis of DHF can be made in the setting of heart failure in a patient with a normal ejection fraction.
Order echocardiography within 72 hours of symptom onset
A major challenge for clinicians is to determine whether a patient’s dyspnea is a true symptom of heart failure. Signs and symptoms of heart failure must be defined using clinical indicators such as the Framingham heart failure criteria (FIGURE).26 Diagnosis of heart failure is more easily made for a patient presenting to the emergency department with acute pulmonary edema than it is for an outpatient seen repeatedly for shortness of breath over months.
For a patient presenting with acute pulmonary edema, an echocardiogram should be performed within 72 hours of symptoms to document cardiac function in proximity to the heart failure exacerbation. The ejection fraction of patients with DHF can remain within normal range, even during acute decompensation.27,28 Stroke volume and cardiac output may be decreased despite a normal ejection fraction.
Cardiogenic pulmonary edema in DHF patients results from the stiffened ventricle’s inability to compensate for increased venous return due to an expansion in central blood volume or sodium retention. Subsequently, diastolic pressures elevate and impede lung compliance, which increases the work of breathing and dyspnea.20,29 A normal ejection fraction and symptom diminishment following diuresis in the setting of acute decompensation help confirm the diagnosis of DHF, especially when other disease states are complicating the clinical picture.30
Elevated BNP levels may be helpful
An elevated level of b-type natriuretic peptide (BNP) can help confirm the clinical diagnosis of heart failure, and it has been shown in small studies to be a valid marker of DHF.31,32 In a study of 294 patients referred for echocardiography to evaluate LV function, Lubien et al found that a BNP value of at least 62 pg/mL had a sensitivity of 85%, a specificity of 83%, and an accuracy of 84% for heart failure in patients with a normal ejection fraction.32 All patients with systolic dysfunction defined by an ejection fraction <50% were excluded from this study. These results, though promising, must be confirmed by further studies evaluating the diagnostic utility of BNP to detect active heart failure symptoms in patients with diastolic dysfunction.
Treatment of symptomatic diastolic dysfunction
For SHF patients, multiple large outcome trials have clearly documented the benefit of angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, and aldosterone antagonists in reducing mortality.33-36 The relative paucity of outcome data for DHF has resulted in medical therapy primarily centered on modifying physiologic factors to improve LV filling and relaxation. Specifically, treatment should focus on symptom reduction, balancing fluid status, controlling heart rate, decreasing any ischemia, and achieving blood pressure goals.19,20,22,31 Though many of the medications used to treat SHF are also used for DHF, there are several important differences in appropriate initiation and subsequent titration of these drugs in the 2 settings.20,31
While treatment of DHF is largely theoretical, a limited number of well-designed, randomized studies are available to help determine appropriate therapy.37-39TABLE 4 provides a summary of the evidence base for evaluation and treatment of systolic vs diastolic heart failure.40TABLE 5 gives a synopsis of these studies. A suggested diagnostic and treatment approach for patients with DHF is outlined in the FIGURE. After determining whether a patient has DHF— primarily through the ruling out of other conditions and confirmation with echocardiographic studies—consider the applicability of each treatment based on a patient’s medical history and present condition.
TABLE 4
Comparative evidence base for evaluation and treatment of systolic vs diastolic heart failure