Correlation Between the Ventricular Electrogram Amplitude in Sinus Rhythm and in Ventricular Fihrillation JAMES W. LEITCH, RAYMOND YEE, GEORGE ]. KLEIN, DOUGLAS L. JONES, and GHALLON ]. MURDOGK From the Cardiac Investigation Unit, University Hospital, London, Ontario, Canada LEITCH, J.W., ET AL.: Correlation Between the Ventricular Electrogram Amplitude in Sinus Rhythm
and in Ventricular Eihrillation. During testing of implantable defibriUators, abiUty to sense ventricular jibrillafion is assessed by observing electrograms and the emitted ECG interpretation channel during induced ventricular jibrilJation. We hypothesized that ventricular eJectrogram amplitude in sinus rhythm could be used to predict the ventricular eJectrogram amplitude in ventricular/lbriJlation and serve as a first approximation of the "safety margin" for sensing ventricular jibrillafion. We compared the peak-topeak epicardiaJ ventricuJar electrogram during sinus rhythm and ventricular jibrilJation in 12 patients undergoing defibrillator implantation. The ventricular eJectrogram was recorded with an integrated bipolar lead and filtered at 10-50 Hz. VentricuJar jibriJJation was induced by aJternating current and the ventricuJar eJectrogram measured from cessation of alternating current to the first countershock. The mean ventricuJar eJectrogram ampJitude in sinus rhythm was 15.3 ± 5.4 mV (range 7.1-25.5} and in 37 episodes o/ventricular fibriJJation was 8.3 ± 3.6 mV (range 2.1-16.3). There was a significant relationship between the mean ventricuJar eJectrogram amplitude in sinus rhythm and in ventricular jibriJJation (R = 0.7, P < 0.001). There was wide variation among individuals in the decrease in the mean ventricular electrogram amplitude during ventricular fibrillation, with the ratio of mean ventricular electrogram in sinus rhythm to mean ventricular electrogram in ventricular fibrillation ranging from 0.29 to 1.05 (mean 0.55 ± 0.20]. This suggests that up to a fourfold decrease may be expected in the mean ventricular electrogram amplitude during ventricular fibrillation. These results suggest that there is a relationship between the mean ventricular electrogram in sinus rhythm and in ventricular fibrillation which is useful as an initial approximation in assessing sensing lead function and programming device sensitivity levels. [PACE, Vol. 13, September 1990} ventricuJar jibriJIation, impJantable dejibriJIator Introduction Reliable detection of ventricular fibrillation by implanted defibrillators requires tbat the devices be able to sense ventricular electrograms of sufficient amplitude during the tachyarrhythmia. While ventricular electrogram amplitude from tbe sensing electrodes is routinely measured during sinus rhythm, an adequate ventricular electrogram amplitude during ventricular fibrillation
Supported by the Ontario Heart and Stroke Foundation. Address for reprints: Raymond Yee. MD, FRCP(C), FACC. Cardiac Investigation Unit, University Hospital, 339 Windermere Rd., London, Ontario. N6A 5A5. Received December 4, 1989; Revision April 9, 1990; Accepted lune 27, 1990.
PACE, Vol. 13
is best assessed by observing the emitted marker pulses and ventricular electrogram during intraoperative testing. We hypothesized that tbe ventricular electrogram amplitude in sinus rhytbm could also be used to predict tbe ventricular electrogram amplitude during ventricular fibrillation and thus provide an additional guide to the device's ability to sense in ventricular fibrillation. Tbe purpose of this study was to compare ventricular electrogram amplitude in sinus rhytbm and in ventricular fibrillation in a consecutive series of patients undergoing defibrillator implantation. Methods Twelve consecutive patients undergoing implantation of an epicardial patch defibrillator sys-
September 1990
1105
LEITCH. ET AL.
tern underwent this study. Informed consent for implantation and perioperative testing was obtained. At defibrillator implantation, three epicardial patches and a pace/sense electrode were fixed to the heart as described previously.' The pace/sense screw-in electrode (Medtronic model 6917A 53T, surface area 6.6 mm^ [Medtronic. Inc., Minneapolis, MN, USAD was placed 1-2 cm adjacent to the large patch (Medtronic model 6897L, defibrillation coil surface area 870 mm^) in the left ventricular free wall. The screw-in electrode served as the cathode and the large patch as the anode for the sensing electrode pair. The screw-in electrode was repositioned if the sensed ventricular electrogram amplitude in sinus rhythm was
and in Ventricular Eihrillation. During testing of implantable defibriUators, abiUty to sense ventricular jibrillafion is assessed by observing electrograms and the emitted ECG interpretation channel during induced ventricular jibrilJation. We hypothesized that ventricular eJectrogram amplitude in sinus rhythm could be used to predict the ventricular eJectrogram amplitude in ventricular/lbriJlation and serve as a first approximation of the "safety margin" for sensing ventricular jibrillafion. We compared the peak-topeak epicardiaJ ventricuJar electrogram during sinus rhythm and ventricular jibrilJation in 12 patients undergoing defibrillator implantation. The ventricular eJectrogram was recorded with an integrated bipolar lead and filtered at 10-50 Hz. VentricuJar jibriJJation was induced by aJternating current and the ventricuJar eJectrogram measured from cessation of alternating current to the first countershock. The mean ventricuJar eJectrogram ampJitude in sinus rhythm was 15.3 ± 5.4 mV (range 7.1-25.5} and in 37 episodes o/ventricular fibriJJation was 8.3 ± 3.6 mV (range 2.1-16.3). There was a significant relationship between the mean ventricuJar eJectrogram amplitude in sinus rhythm and in ventricular jibriJJation (R = 0.7, P < 0.001). There was wide variation among individuals in the decrease in the mean ventricular electrogram amplitude during ventricular fibrillation, with the ratio of mean ventricular electrogram in sinus rhythm to mean ventricular electrogram in ventricular fibrillation ranging from 0.29 to 1.05 (mean 0.55 ± 0.20]. This suggests that up to a fourfold decrease may be expected in the mean ventricular electrogram amplitude during ventricular fibrillation. These results suggest that there is a relationship between the mean ventricular electrogram in sinus rhythm and in ventricular fibrillation which is useful as an initial approximation in assessing sensing lead function and programming device sensitivity levels. [PACE, Vol. 13, September 1990} ventricuJar jibriJIation, impJantable dejibriJIator Introduction Reliable detection of ventricular fibrillation by implanted defibrillators requires tbat the devices be able to sense ventricular electrograms of sufficient amplitude during the tachyarrhythmia. While ventricular electrogram amplitude from tbe sensing electrodes is routinely measured during sinus rhythm, an adequate ventricular electrogram amplitude during ventricular fibrillation
Supported by the Ontario Heart and Stroke Foundation. Address for reprints: Raymond Yee. MD, FRCP(C), FACC. Cardiac Investigation Unit, University Hospital, 339 Windermere Rd., London, Ontario. N6A 5A5. Received December 4, 1989; Revision April 9, 1990; Accepted lune 27, 1990.
PACE, Vol. 13
is best assessed by observing the emitted marker pulses and ventricular electrogram during intraoperative testing. We hypothesized that tbe ventricular electrogram amplitude in sinus rhytbm could also be used to predict tbe ventricular electrogram amplitude during ventricular fibrillation and thus provide an additional guide to the device's ability to sense in ventricular fibrillation. Tbe purpose of this study was to compare ventricular electrogram amplitude in sinus rhytbm and in ventricular fibrillation in a consecutive series of patients undergoing defibrillator implantation. Methods Twelve consecutive patients undergoing implantation of an epicardial patch defibrillator sys-
September 1990
1105
LEITCH. ET AL.
tern underwent this study. Informed consent for implantation and perioperative testing was obtained. At defibrillator implantation, three epicardial patches and a pace/sense electrode were fixed to the heart as described previously.' The pace/sense screw-in electrode (Medtronic model 6917A 53T, surface area 6.6 mm^ [Medtronic. Inc., Minneapolis, MN, USAD was placed 1-2 cm adjacent to the large patch (Medtronic model 6897L, defibrillation coil surface area 870 mm^) in the left ventricular free wall. The screw-in electrode served as the cathode and the large patch as the anode for the sensing electrode pair. The screw-in electrode was repositioned if the sensed ventricular electrogram amplitude in sinus rhythm was
