Predicting Recovery of Heart Muscle Strength after a Heart Attack

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The summary below is from the full report titled "Recovery of Ventricular Function after Myocardial Infarction in the Reperfusion Era: The Healing and Early Afterload Reducing Therapy Study." It is in the 20 March 2001 issue of Annals of Internal Medicine (volume 134, pages 451-458). The authors are SD Solomon, RJ Glynn, S Greaves, U Ajani, J-L Rouleau, F Menapace, JMO Arnold, C Hennekens, and MA Pfeffer.

What is the problem and what is known about it so far?

Severe blockage of the arteries that supply blood to heart muscle is known as a heart attack (the medical term is "myocardial infarction"). Heart muscle is weakened immediately after a heart attack but gradually regains its strength. Occasionally, the heart muscle progressively weakens, leading to chronic failure of the heart to work as an efficient pump. Although several techniques and drugs are used to improve blood flow to heart muscle rapidly after a heart attack (known as reperfusion therapy), the factors that influence development or improvement of heart muscle weakness are not known.

Why did the researchers do this particular study?

To see whether clinical or laboratory test characteristics can predict recovery of heart muscle strength after a heart attack.

Who was studied?

249 patients with heart attacks who had undergone reperfusion therapy. These patients had taken part in a separate study of treatment with several different doses of a drug that reduces the workload on the heart (the Healing and Early Afterload Reduction Therapy [HEART] study).

How was the study done?

The researchers reanalyzed data from the HEART study, including clinical characteristics; blood tests for creatine kinase (CK); and the results of echocardiography done 1, 14, and 90 days after patients' heart attacks. Creatine kinase is a chemical that spills into the bloodstream when heart muscle cells are damaged. Echocardiography uses sound waves to analyze heart size and muscle function.

What did the researchers find?

Patients with the highest levels of CK in their blood were least likely to have complete recovery of heart muscle strength. In addition, patients with enlargement of the left ventricle (the main pumping chamber of the heart) during the 90-day observation period were less likely to show improvement in overall pumping ability, although a few patients with such enlargement did have improvement. Only 26% of patients with any degree of left ventricular enlargement recovered complete strength of the heart muscle.

What were the limitations of the study?

The groups that received different doses of the drug that reduces workload of the heart all recovered heart muscle function about equally. The study therefore does not tell us whether drugs of this kind can improve recovery of heart muscle function. Moreover, the researchers could not tell which patients actually achieved reperfusion and which did not. Thus, they could not tell whether successful reperfusion improved recovery of heart muscle strength. Finally, only one type of heart attack was studied; the results of this study may not apply to other types.

What are the implications of the study?

Measuring CK levels in the blood and testing for enlargement of the heart by using echocardiography can help predict which patients will recover heart muscle strength after a heart attack.