Long-Term Effect of Right Ventricular Pacing on Myocardial Perfusion and Function

OBJECTIVES: The purpose of this study was to investigate the effect of long-term ventricular pacing on myocardial perfusion and function in patients receiving such pacing. BACKGROUND: The long-term effect of ventricular pacing on myocardial perfusion and function in humans is unclear, although animal studies have suggested that it may be adverse. METHODS: Forty-three patients with complete heart block and dual-chamber rate-adaptive (DDDR) pacing were studied. All underwent thallium-201 (Tl-201) exercise myocardial scintigraphy to assess myocardial perfusion and radionuclide ventriculography to determine left ventricular function and regional wall motion. Coronary angiography was also performed in patients with abnormal findings on Tl-201 study. RESULTS: There was no significant difference in mean age, gender, percent ventricular pacing, pacing threshold, ventricular pacing output and metabolic equivalents on exercise testing between patients with or without perfusion defects on exercise Tl-201 scintigraphy. However, the duration of pacing tended to be longer in patients with than in those without perfusion defects (43.9 +/- 49.7 vs. 20.1 +/- 9.8 months, p = 0.05). Tl-201 perfusion defects were noted in 28 (65%) of 43 of patients (inferior 78% n = 22, apical 67% n = 17, septal 21% n = 6, anterior 7% n = 2, lateral 3% n = 1). Of 16 of 28 patients with abnormal Tl-201 findings who underwent coronary angiography, only 3 (19%) had significant coronary artery disease. Patients with an abnormal perfusion defect had a significantly lower left ventricular ejection fraction (48.5 +/- 9.9% vs. 59.6 +/- 8.9%, p < 0.001) and a higher percent of wall motion abnormalities (57% vs. 20%, p = 0.026), mainly over apical regions. CONCLUSIONS: Long-term right ventricular apical pacing resulted in a high incidence of myocardial perfusion defects that increased with the duration of pacing. These myocardial perfusion abnormalities were associated with apical wall motion abnormalities and impaired global left ventricular function.