What is the efficacy of myocardial perfusion imaging for cardiac assessment?

Updated: Nov 20, 2018
  • Author: Richard S Krause, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

Answer

Because myocardial perfusion imaging increases the diagnostic accuracy of stress testing, the American College of Cardiology and American Heart Association (ACC/AHA) guidelines recommend that it be used in several patient subsets. Thus, it should be used if there are any baseline ECG abnormalities that would interfere with the measurement of stress-induced ST-segment changes, such as left ventricular hypertrophy (LVH), bundle branch blocks, or digoxin use. In addition, myocardial perfusion imaging should always be used as an adjunct when pharmacologic stress testing is performed. Finally, it is useful in patients at higher risk, such as those with diabetes.

The ACC/AHA guidelines report that when both exercise and pharmacologic stress tests with SPECT imaging are compared to angiography, the test is 87% sensitive and 73% specific for significant stenosis (>50%). [16]

In a 6-year follow-up study of 1,137 patients with normal tl-201 perfusion studies, the annual rate of MI or cardiac death was only 0.88%. [17] In a meta-analysis of 14 trials with over 12,000 patients, normal Tc-99m sestamibi imaging was associated with a cardiac event rate of 0.6% per year. [18]

A difficulty that commonly arises is when there is disagreement between the ECG evidence and myocardial perfusion imaging on a stress test. In a study of 473 patients with chest pain, two-thirds of whom had abnormal ST-segment response on exercise, normal Tc-99m sestamibi SPECT studies were associated with an annual mortality of 0.2%. [19]  Thus, when interpreting stress tests, more significance is generally placed on the myocardial perfusion results than the ECG results. [19]


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