A PROSPECTIVE-STUDY OF CHANGES IN RIGHT VENTRICULAR DP/DT DURING VENTRICULAR-TACHYCARDIA

The automatic implantable cardioverter defibrillator (AICD) has significantly decreased mortality in high risk ventricular tachycardia (VT) patients. The AICD provides treatment based on ventricular rate, sometimes leading to high energy shocks in conscious patients with stable VT, or patients with sinus or supraventricular tachycardia. Other physiological parameters, such as maximal positive and negative systolic right ventricular (RV) dP/dt (RV + dP/dt(max), RV - dP/dt(max), respectively), may be included in detection algorithms for future implantable defibrillators. We studied frequency band limited positive and negative RV dP/dt(max) before, during, and after 13 episodes of VT lasting at least 40 beats in duration in nine male patients. The mean (+/- SEM) RV + dP/dt(max), dropped by 120 +/- 28 mmHg/sec (P < 0.001) during the first five beats of VT. RV + dP/dt(max) then slowly rose toward baseline levels until a significant overshoot occurred during the first ten beats following VT termination (DELTA = 234 +/- 58 mmHg/second, P < 0.002). RV + dP/dt(max) correlated poorly with mean arterial pressure (r = 0.32, P > 0.1), systolic blood pressure (r = 0.19, P > 0.1), and VT cycle length (r = 0.34, P > 0.1). Conversely, RV - dP/dt(max) rose during the first ten beats of VT (74 +/- 27 mmHg/sec, P > 0.05) and then slowly drifted back toward baseline levels. Like RV + dP/dt(max), RV - dP/dt(max) overshot baseline levels during the recovery phase (- 108 +/- 48 mmHg/sec, P < 0.05). RV - dP/dt(max) also did not correlate well with mean arterial pressure (r = 0.06, P > 0.1), systolic blood pressure (r = 0.077, P > 0.1), or VT cycle length (r = 0.064, P > 0.1). We conclude that frequency band limited measurement of positive and negative RV dP/dt(max) poorly reflect hemodynamic stability during VT and would probably not be useful as a hemodynamic sensor in AICDs.