ABSTRACT
Cardiac resynchronization therapy (CRT) has emerged as a method of reducing mortality and increasing ejection fraction in patients with severe left ventricular (LV) disease.1-3 Treatment aimed at resynchronization clearly implies that asynchrony is present in the control state with associated deleterious physiological consequences. CRT was originally developed in patients whose LV disease was associated with severe disturbances of activation, referred to collectively as left bundle branch block (LBBB), in whom predictable relations with asynchrony had been demonstrated. More recently, the technique has been extended to patients in whom the QRS duration is normal4,5 and in whom the basis for any asynchrony is less well defined. However, it has long been known that coronary artery disease (CAD) is frequently associated with disturbances of the timing of regional LV wall motion in the resting state, regardless of QRS duration. Since patients with ischemic heart disease are frequently considered for CRT, we have reviewed the nature of CAD-induced asynchrony and the effect of treatment. We also explore interrelations between QRS duration, pharmacological stress, and CAD, and their separate effects on regional wall motion in detail, since exploiting them may potentially enhance the performance of currently available CRT.
