Aims: Cardiac resynchronization therapy (CRT) utilizing biventricular pacing (BVP) is a promising treatment modality for symptomatic patients with chronic left ventricular (LV) systolic dysfunction and intraventricular conduction delay. Clinical studies have shown short-term improvement in contractile function and mid-term improvement in clinical status with CRT. The objective of this study was to evaluate the haemodynamic consequences of temporary interruption of CRT after long-term stimulation.
Methods and results: Twenty patients (16 men, 4 women) with LV dysfunction and New York Heart Association class III or IV heart failure, despite optimal medical therapy and a QRS interval of at least 120 ms, received a transvenous BVP system at the age of 66 (interquartile range, 61-69). Patients were studied after a median duration of 427 days (interquartile range, 281-563) of continuous CRT and again 72 h after cessation of BVP. Withdrawal of CRT resulted in a significant decline in maximal rate of LV systolic pressure rise from 711 mmHg/s (interquartile range, 640-816) to 442 mmHg/s (interquartile range, 389-582) (P=0.0001) and increases in mitral effective regurgitant orifice area from 4.8 mm(2) (interquartile range, 0.0-7.8) to 9.1 mm(2) (interquartile range, 5.7-13.3) (P=0.0001), mitral regurgitant volume from 7.8 mL (interquartile range, 0.0-11.5) to 16.0 mL (interquartile range, 10.7-20.8) (P=0.0001) and fraction from 13.8% (interquartile range, 0.0-19.2) to 27.7% (interquartile range, 14.6-34.0) (P=0.0002) determined by Doppler echocardiography.
Conclusion: Cessation of long-term BVP leads to a decline in LV systolic performance and an increase in functional mitral regurgitation. These results indicate a sustained benefit of long-term CRT and support the notion to maintain CRT indefinitely.