Impedance cardiography: a useful and reliable tool in optimization of cardiac resynchronization devices

摘要

Aims Optimizing cardiac resynchronization therapy (CRT) devices has become more complex since modification of both atrioventricular (AV) and interventricular (W) stimulation intervals has become possible. The current paper presents data from the routine use of impedance cardiography (IC)-based cardiac output (CO) measurements to guide the optimization of AV- and W-interval timing of CRT devices. Methods and results Forty-six patients with heart failure (left ventricular ejection fraction < 35%, New York Heart Asociation (NYHA) lll桰V) and left bundle branch block (>130 ms) in sinus rhythm were evaluated 3-5 days after implantation of a CRT device by means of IC. CO was measured without pacing and with biven-tricular pacing using a standard protocol of W- and AV-interval modification from -60 to +-60 ms and 80 to 140 ms, respectively, in 20 ms steps. Mean CO without pacing was 3.66 +- 0.85 L/min and significantly increased to 4.40 +-1.1 L/min (P< 0.05) with simultaneous biventricular pacing and an AV interval of 120 ms. Optimizing' both W and AV intervals further increased CO to 4.86 +- 1.1 L/min (P<0.05). Maximum CO was measured in most patients with left ventricular pre-excitation. The proportion of 'non-responders' to CRT was reduced by 56% following AV- and W-interval modification using IC guidance. Conclusion Modification of both AV and W intervals in patients with a CRT device significantly improves CO compared with standard simultaneous biventricular pacing and no pacing. IC is a useful non-invasive technique for guiding this modification. Marked variability of optimal AV and W intervals between patients requires optimization of these intervals for each patient individually.