Each heartbeat has a systolic component and a diastolic component. The heart first contracts and pumps blood out of the ventricular chambers (Systolic phase) and then goes through a phase of relaxation which allows blood to refill the ventricles (Diastolic Phase). According to this report, even when the systolic function is normal, diastolic dysfunction (DD) has been associated with an increased risk of death from cardiovascular and other reasons. The researchers in this study attempted to determine if the mortality risk associated with DD was an independent risk factor for increased risk for death in the presence of a normal systolic function. They also set out to determine whether this held true for milder cases of DD as well. The researchers began to understand the clinical relevance of the presence of diastolic dysfunction and degree of DD in patients who had normal ejection fraction who underwent outpatient echocardiography. They used echocardiography since it is one of the most common cardiac non-invasive imaging tests in the United States.
Researchers from the Cleveland Clinic that included Dr. Carmel M. Halley, MD and his colleagues studied clinical records and electrocardiograms of 36,261 patients who had attended the Cleveland Clinic between 1996 and 2005 and had demonstrated a normal systolic function. The researchers then started collecting information on diastolic function in these patients, if any. If DD was found, it was graded as mild, moderate or severe.
The researchers determined rates of cardiovascular disease in the study population. This included congestive heart failure (3.5 percent), coronary artery disease (0.6 percent) and peripheral vascular disease (1.1 percent). DD was found in most of the patients that were studied. A total of 65.2 percent of patients had some degree of DD. When graded, it was revealed that 60.0 percent had mild DD, 4.8 percent had moderate DD, and 0.6 percent had severe DD. These patients were followed for an average of 6.2 years. During the follow up phase, 5,789 deaths occurred. It was found that the adjusted mortality rate was higher in patients with worsening DD. There were 4,469 deaths [21 percent] in the mild DD cohort, 429 deaths [24 percent] in the moderate DD cohort, and 49 deaths [39 percent] in the severe DD cohort. Nonetheless, when propensity matching techniques were applied during statistical analysis of the data, it was revealed that only moderate and severe DD were related to an increased mortality risk.
The authors note that since the prevalence of DD was so high in their study population, most patients who presented to the outpatient electrocardiographic testing had, by definition, preclinical DD. This is of great clinical relevance since DD can provide the physician with prognostic clues. Since in most cases, the electrocardiograms are ordered by non-cardiologists, this information is of particular importance. The researchers have pressed the need for more research to understand how DD increases the risk of mortality as an independent factor. They also added that the results of this study indicate that increased awareness about the clinical significance of moderate and severe DD may help in triaging patients who may be at a higher risk of dying from DD even if systolic function is preserved. This could be of particular importance when DD is at a preclinical stage.
Commentary: A Piece of the PuzzleThere is a commentary accompanying the published study which looks at the prevalence of DD in the face of a preserved systolic function in patients with heart failure (HF) admitted in U.S hospitals. More than 60 percent of patients with HF admitted had DD with normal systolic function. Dr. Ileana L. Piña, M.D., M.P.H., from Case Western Reserve University in Cleveland writes that the pathophysiology of DD is not completely understood. She states that she would like to understand if DD could exist without progressing to HF, and if the physician successfully identified DD in a patient with mild or no symptoms, would the patient progress to overt HF and have a higher mortality risk.
Dr. Piña in her report, while critically analyzing this study, describes the continuum from mild, asymptomatic cases of DD to severe symptomatic cases as a puzzle. Dr. Piña points out the women selected in the study were younger in this study as compared to others. She also points out that the incidence of HF was quite low in the study population that was evaluated. She, however, notes that it does provide more evidence that HF with normal systolic function is a complex disorder and with increasing complexity in how patients eventually progress to frank HF. She also would like to understand the relationship between electrocardiographic findings of DD for older women who present with acute symptoms of HF with preserved systolic function. She writes that more research in this area will help us understand these medical puzzles.
Link to Abstract of Study