Diastolic dysfunction of the heart associated with increased risk of death, study finds

During each heartbeat, the heart contracts (pumping blood out, a phase called systole) and then relaxes (allowing the heart chambers to refill with blood, a phase called diastole). Diastolic dysfunction (DD), which occurs when the relaxation phase of this cardiac cycle is impaired, has been associated with an increased risk of death from cardiovascular and other causes, sometimes when systolic function is normal, according to background information in the article. The authors sought to determine whether the mortality risk associated with DD was independent of other cardiovascular conditions or systolic function, and whether the risk existed for mild cases. "We therefore sought to address the clinical relevance of the presence of DD and the degree of DD in patients with normal ejection fraction undergoing outpatient echocardiography, one of the most commonly used cardiac noninvasive imaging tests in the United States," they write.

Carmel M. Halley, M.D., and colleagues from the Cleveland Clinic studied the clinical records and echocardiographic findings of 36,261 patients who, between 1996 and 2005, had an outpatient echocardiogram that revealed normal systolic function. Researchers then determined whether patients' diastolic function was normal or abnormal, and graded cases of DD as mild, moderate, or severe.

Rates of established cardiovascular disease were low in the study population, including congestive heart failure (3.5 percent), coronary artery disease (0.6 percent) and peripheral vascular disease (1.1 percent). Most of the patients (65.2 percent) had some degree of DD; 60.0 percent of cases were mild, 4.8 percent were moderate, and 0.4 percent were severe. During an average followup time of 6.2 years, 5,789 deaths occurred, and the unadjusted mortality rate was higher in patients with worsening degrees of DD (4,469 deaths [21 percent] in the mild DD group, 429 deaths [24 percent] in the moderate DD group and 49 deaths [39 percent] in the severe DD group). However, in statistical analysis using propensity matching techniques, only moderate and severe DD were associated with an increased mortality risk.

"Because the overall prevalence of DD was high, most patients who presented for outpatient echocardiographic testing in our institution had, by definition, preclinical DD," the authors note. In this regard, the study "provides the physician with a prognostic context when DD is reported," particularly because in most cases, noncardiologists are ordering the echocardiographic procedures. The researchers call for further investigation about how moderate and severe DD raise the risk of mortality. "However," they add, "our results suggest that an increased awareness of the clinical significance of advanced DD may lead to earlier identification of those patients who are at risk, especially at a preclinical stage."

Commentary: A Piece of the Puzzle

Of U.S. patients admitted to hospitals for heart failure (HF), more than two in five have diastolic dysfunction and preserved systolic function, according to a commentary accompanying the article. There is still a gap in the understanding of this condition's pathophysiology, writes Ileana L. Piña, M.D., M.P.H., from Case Western Reserve University in Cleveland. "Does DD exist that does not progress to HF? If the physician identifies DD in a patient with mild or no symptoms, will that patient progress to frank heart failure and have a higher mortality risk?"

Describing the continuum from mild, asymptomatic cases of DD to severe, symptomatic cases as "a puzzle," Piña also discusses how women with DD fare, and points out that women in the study by Halley and colleagues were younger than those in other studies, and the incidence of HF in the database they drew from is low. However, she notes that "These observations lend credence to the complexity of [HF with normal systolic function] beyond mere DD and of the ways patients ultimately progress to frank HF," Piña writes. "The missing link between DD diagnosed via echocardiographic testing and the acute presentation of older women with [this condition] is yet to be elucidated. Further work will help solve this puzzle."