LETTER TO THE EDITOR
Specificity of noninvasive pacemaker stress echocardiography in diagnosis of coronary artery disease
Prof. Panos E. Vardas, MD, PhD, FESC, FACC and
Emmanuel I. Skalidis, MD
Cardiology Department, Heraklion University Hospital, P.O. Box 1352 71110, Heraklion, Greece
cardio{at}med.uoc.gr
We read with great interest the recently published study by Picano et al. (1) in the October 2, 2002, issue of JACC. The investigators concluded that noninvasive pacemaker stress echocardiography is a diagnostically efficient method for patients with a permanent pacemaker and suspected or known coronary artery disease (CAD).
Nevertheless, some concerns arise based on our experience and from careful review of the published reports.
First, the main problem in detecting CAD in patients with permanent ventricular pacing is the low specificity of noninvasive techniques related to abnormalities of microvascular flow arising from chronic functional and/or structural abnormalities induced by abnormal ventricular excitation (2). We do not believe that the study by Picano et al. (1) could solve this problem; the studied group consisted of patients with a high prevalence of risk factors for CAD (>50%) and/or previous myocardial infarction (37%): it was, therefore, an excellent way to assess the sensitivity of the method, but not the specificity. In addition, 15 of 45 patients were in AAI pacing mode, and even for the remaining patients we do not know if there was partial or full ventricular excitation from the pacemaker electrode during daily life or during the stress protocol. We also do not know whether the studied group represents a total population of patients with a pacemaker, as the manner of the patients’ recruitment is unclear.
Second, the allegation that perfusion defects are more common than wall motion abnormalities during stress in patients with alterations of coronary flow reserve and normal epicardial coronary arteries conflicts with the findings of a study by Tse et al. (3), who observed wall motion abnormalities by radionuclide ventriculography to occur in the same proportion of patients with permanent ventricular stimulation and no significant CAD as did perfusion defects detected by dipyridamole thallium myocardial scintigraphy. Thus, the advantage of the stress echocardiogram remains in question.
Third, given the deterioration of myocardial perfusion over time that is observed in some studies (3,4), it is crucial to know the mean duration of pacing, especially in patients without wall motion abnormalities. Such data were not provided in the study by Picano et al. (1).
In conclusion, although no one has doubt about the diagnostic accuracy of the noninvasive pacemaker stress echocardiogram in patients with AAI pacing mode, or, more generally, about the sensitivity of the same method in detecting CAD, the specificity of the method remains in doubt. Based on data currently available, a specificity of 50% is the best we can expect from noninvasive techniques (2–5), at least in patients with permanent ventricular stimulation.
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References
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- Picano E, Alaimo A, Chubuchny V, et al. Noninvasive pacemaker stress echocardiography for diagnosis of coronary artery disease. J Am Coll Cardiol. 2002;40:1305–1310[Abstract/Free Full Text]
- Skalidis EI, Kochiadakis GE, Koukouraki SI, et al. Myocardial perfusion in patients with permanent ventricular pacing and normal coronary arteries. J Am Coll Cardiol. 2001;37:124–129[Abstract/Free Full Text]
- Tse HF, Yu C, Wong KK, et al. Functional abnormalities in patients with permanent right ventricular pacing. The effect of sites of electrical stimulation. J Am Coll Cardiol. 2002;40:1451–1458[Abstract/Free Full Text]
- Tse HF, Lau CP. Long-term effect of right ventricular pacing on myocardial perfusion and function. J Am Coll Cardiol. 1997;29:744–749[Abstract]
- Lakkis NM, He ZX, Verani MS. Diagnosis of coronary artery disease by exercise thallium-201 tomography in patients with a right ventricular pacemaker. J Am Coll Cardiol. 1997;29:1221–1225[Abstract]
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