Left atrium neasurements may predict future for heart attack patients

Ultrasound measurements of the volume of the left atrium taken soon after a heart attack can help physicians predict a patient’s five-year mortality rate, according to a new study in the July 21, 2004 issue of the Journal of the American College of Cardiology.

“Increased left atrial volume index is an important risk factor for long-term survival in echocardiograms performed early in patients with acute myocardial infarction (heart attack). Left atrial volume assessment by echo should be an integral part of routine echocardiograms, being preferable to the current commonly-reported left atrial diameter, which does not reflect left atrial dimension accurately enough to serve as an independent prognostic risk factor,” said Micha S. Feinberg, MD, FACC with the Chaim Sheba Medical Center in Tel Hashomer, Israel.

The research team, including lead author Roy Beinart, MD, studied 395 consecutive heart attack patients who were treated at the Chaim Sheba Medical Center and the Rabin Medical Center in Petach Tiqvah, Israel during 1996. All the patients underwent ultrasound examinations of their hearts within 48 hours of admission, including measurements of the left atrium.

More than a third (34.5 percent) of heart attack patients with left atrial volume indexes larger than 32 milliliters per meter squared had died within five years, compared to 14.2 percent of the patients with smaller left atrial volumes. The researchers wrote that in this study left atrial volume was a better predictor of death rates than left ventricular volume and mitral valve regurgitation.

Dr. Feinberg said that left atrial volume appears to be an indication of the long-term cumulative effects of heart disease, and so it may be a more stable indicator than acute changes, such as left ventricular function, that are measured at the time of a heart attack.

“As patient awareness increases, and early hospital help and early interventions become more available (including percutaneous coronary interventions, such as angioplasty and stents), the impact of acute insults diminishes. All these issues make the assessment of indicators of prior insults more important for the long term. Early left ventricular functional assessment may overestimate the true final insult of the heart. Left atrial volume is a common pathway that reflects prior insults to the heart, the ‘diastolic memory’ of the heart, and is less influenced by acute hemodynamic changes that may be transient,” Dr. Feinberg said.

He said this study went beyond earlier research.

“Our study had a five-year follow up, data were collected prospectively, and the echo studies were all performed early, usually within 24 hours (and no later than 48 hours) of admission. Left ventricular volume was included in the analysis and left atrial volume was determined from a single plane (a simplified method),” Dr. Feinberg said.

Dr. Feinberg said future studies should look at whether three-dimensional ultrasound imaging is more accurate than the two-dimensional technique used in this study. He also noted that this study looked at measurements taken shortly after a heart attack, and so the findings may not apply to comparisons of other heart function and structure measurements at later stages of recovery.

Nelson B. Schiller, MD, FACC at the University of California in San Francisco, who was not connected with this study, said the left atrium is as unexplored as the depths of the ocean and the results of this study highlight the value of adding a relatively simple step to echocardiography examinations of heart attack patients.

“The study by Beinart et al. confirms that minimal additional effort expended in quantitating the volume index of the left atrium in echocardiograms from patients with myocardial infarction (heart attack) is rewarded with powerful information about prognosis. Increases in left atrial volume index beyond the normal range, not readily apparent by simple inspection of the echocardiogram, double the chances of a patient developing congestive heart failure and increase five-year mortality two-and-one-half-fold,” Dr. Schiller said.

“Our long experience in applying left atrial volume index clinically suggests that the power of this measurement is not limited to myocardial infarction but to practically every important cardiac disease. The results of the study of Beinart et al. should encourage practitioners who use echocardiography to add exploration of the depths of the left atrium to routine practice and to use the trove of recovered data to identify patients warranting the most intense clinical navigation,” he added.

The American College of Cardiology, a 29,000-member nonprofit professional medical society and teaching institution, is dedicated to fostering optimal cardiovascular care and disease prevention through professional education, promotion of research, leadership in the development of standards and guidelines, and the formulation of health care policy.

http://www.acc.org

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