Predictor of underlying myocardial damage in normally functioning left ventricle with narrow QRS complex: relationship between QRS duration at right ventricle pacing and iodine-123 metaiodobenzylguanidine myocardial scintigraphy.

Objective: Washout rate of iodine-123 metaiodobenzylguanidine (MIBG) myocardial scintigraphy is correlated with the degree of myocardial damage. The aim of this study is to ascertain whether there is any relationship between QRS complex duration at right ventricle (RV) pacing and the degree of myocardial damage assessed by I-123 MIBG myocardial scintigraphy in normally functioning left ventricle.

Methods: The study included 22 patients (10 men and 12 women, ranging in age from 48 to 89 years), with atrioventricular (AV) block (n = 15) and sick sinus syndrome (n = 7). All patients had baseline QRS duration of less than 120 ms and received implantation of a DDD-mode permanent pacemaker. Iodine-123 MIBG myocardial scintigraphy was performed before the pacemaker implantation, and QRS duration at RV pacing at a rate of 70 ppm was calculated immediately after the implantation.

Results: With the use of RV pacing, QRS duration was prolonged ranging from 122.4 to 185.6 ms with a mean of 153.2 +/- 15.2 ms. Washout rate of I-123 MIBG myocardial scintigraphy (WR) was calculated as ranging from 5.0 to 83.0% with a mean of 44.2 +/- 17.5%. There was a strong correlation between WR and QRS duration at RV pacing (r = 0.735, p < 0.001).

Conclusions: It was confirmed that WR of I-123 MIBG was correlated positively with QRS duration at RV pacing. Measurement of QRS duration may be helpful to evaluate the degree of underlying myocardial damage even in the normally functioning left ventricle.