Risk Factors for CHF Exacerbations
Abstract & Commentary
Synopsis: Potentially preventable risk factors can be identified before a CHF exacerbation.
Source: Tsuyuki RT, et al. Arch Intern Med. 2001;161: 2337-2342.
Using the database of the randomized evaluation of Strategies for Left Ventricular Dysfunction (RESOLVD) Pilot Study, Tsuyuki and colleagues set out to determine what exactly precipitated exacerbations of congestive heart failure (CHF) in their patients.
RESOLVD enrolled 768 patients with symptomatic CHF into a double-blind, randomized, 2-stage, multicenter trial. To enter the trial, the patients had to be New York Heart Association functional class II-IV, have an ejection fraction less than 40%, and have a 6-minute walk distance of less than 500 meters. In the first stage of the trial, patients were randomized to an angiotensin II receptor blocker (candesartan), and angiotensin-converting enzyme inhibitor (enalapril), or both. In the second stage, controlled-release metoprolol or placebo was added. The study spanned 43 weeks. Whenever a patient experienced an exacerbation of CHF, investigators completed a CHF Event Form. On this form, they recorded the signs and symptoms of CHF, their plans, and what factors they thought contributed to the exacerbation.
Of the 768 patients enrolled in the study, 180 had 1 or more exacerbations during the study period. The patients who experienced an exacerbation were similar to those who did not, except that there were proportionately more patients in functional class III in the former group. These patients also had more peripheral edema and jugular venous distention (JVD) at baseline. In the 2 days before an exacerbation, 92% of patients were on loop diuretics, 76% on digoxin, 52% on aspirin, 47% on nitrates, and 14% on b-blockers. They gained on average 1.16 kg (2 ½ lbs.). Their physical examinations had the typical findings of lung crackles (66%), JVD (55%), peripheral edema (52%), and third heart sound (36%). Five patients died.
The physicians treating these patients tried to assign cause to the exacerbations. The most commonly identified factors were excessive salt intake (22%); other noncardiac disorders, primarily upper respiratory infections and pneumonia (20%); use of study medications, usually metoprolol (15%); arrhythmia (13%); calcium channel blockers (13%); and inappropriate reductions in CHF therapy (10%). Surprisingly, noncompliance, uncontrolled hypertension, and coronary ischemia were identified in less than 10% of cases.
Tsuyuki et al recommend attending to prevention (ie, education about salt intake and influenza and pneumococcal vaccination) and avoidance of negative inotropic medications as ways to forestall CHF deterioration. They also recommend that CHF patients weigh themselves daily and report any increase, since in their experience, most patients had seemingly minor increases before their exacerbations.
Comment by Allan Wilke, MD
A weakness of this study is that Tsuyuki et al assigned what they thought were "the factors to have contributed to the episode." It is not unusual for a physician to misclassify diagnosis. When I review an article, one of the first questions I ask myself is, "Are these patients similar to mine?" In a few ways, they are not. They were highly selected. All of these patients were on either an ACE inhibitor or an ARB. Despite this being a recommendation for CHF patients,1 not all of mine are. Many were also on a b-blocker, another recommendation.2 These patients were volunteers, and presumably more interested in their disease and probably more knowledgeable and compliant with their medications than mine. In other words, these were near perfect patients. If you see the glass "half-full," as I do, we have a remarkable opportunity here to improve the health of our CHF patients.
References
1. The SOLVD Investigators. N Engl J Med. 1991;325: 293-302.
2. Chavey WE. Am Fam Physician. 2000;62:2453-2462.
Dr. Wilke is an Assistant Professor of Family Medicine, Medical College of Ohio, Toledo, Ohio.
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