Treatment and Outcomes of Heart Attacks in People with Pacemakers

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The summary below is from the full report titled "Treatment of Patients with Myocardial Infarction Who Present with a Paced Rhythm." It is in the 17 April 2001 issue of Annals of Internal Medicine (volume 134, pages 644-651). The authors are SS Rathore, KP Weinfurt, BJ Gersh, WJ Oetgen, KA Schulman, and AJ Solomon.

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

Some people have problems with their heart rhythms. Pacemakers are electronic devices used to help the heart beat more normally. The heartbeat produced by the pacemaker, which is called a "paced rhythm," can be seen on the heart tracings (called electrocardiograms, or ECGs), used to diagnose heart conditions. Heart problems that would normally be detected with ECGs are occasionally missed in patients with pacemakers because the tracing shows only the paced rhythm and not the other heart problems. A heart attack, also known as a myocardial infarction, is caused by blockage of the arteries that supply blood to the heart. Heart attacks are usually detected with an ECG tracing. It is not known, however, whether people who have heart attacks but also have a paced rhythm do worse than people with heart attacks but have no pacemaker and no paced rhythm.

Why did the researchers do this particular study?

To compare treatments and outcomes of heart attacks among people who did or did not have paced rhythms on their initial ECGs.

Who was studied?

The study included 102,249 men and women 65 years and older with myocardial infarction.

How was the study done?

The researchers used routine data from the medical charts of Medicare patients discharged from nongovernmental U.S. hospitals between 1994 and 1996 with a diagnosis of acute myocardial infarction. Types of treatments (drugs and procedures) that patients received were noted, and survival was assessed at 1 month and 1 year.

What did the researchers find?

About 2% of the patients with heart attacks presented with paced rhythms. Paced patients were less likely than others to receive drug therapies now considered standard for most people with heart attacks, such as aspirin and ß-blockers. Paced patients also had fewer procedures that might have helped restore blood flow to the heart. At 3 months, more patients with paced rhythms (26%) had died than other patients (21%). At 1 year, 47% of the patients with paced rhythms had died compared with 36% of other patients.

What were the limitations of the study?

The study was done after the patients had their heart attacks rather than during their illness, and it relied primarily on data recorded in medical records, which are sometimes incomplete. Patients with paced rhythms might have had more serious heart disease to begin with, but the reasons for differences in treatments and outcomes could not be explored in detail.

What are the implications of the study?

Older people with pacemakers and paced rhythms on their ECGs are less likely than others to receive standard treatments for heart attack; they also have poorer survival outcomes than people without paced rhythms at the time of heart attack.