Pacing Protocol - BME Department, Johns Hopkins

Pacing Project

Studying Different Pacing Patterns on Isolated Perfused Rabbit Hearts

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Purpose:

To study the effects of long term pacing with various waveforms on Heart Performance.

i.e. pressure generated in the Left Ventricle.

History:

Previous trials were inconclusive
Short term pacing in rabbit heats has shown no effect
Long term pacing in dogs (MRI) experiments has shown differences

What we are looking for:

Pressure changes in Left Ventricle over longterm pacing
Changes in filling time

Experimental Variables:

Introduction of Millar Pressure Transducer
Placement of Recording Electrodes on the heart
Various shapes of Pacing Waveforms
3 Channel syncronized recording:

ECG
Stimulation
Pressure

# of iterations per setting

Pacing Voltage
Pacing Pulse Duration
Coupling inteveral

ECG Amplification
Sampling Rate

Pacing Protocol:

Langendorff Experiment - isolated rabbit hearts
Various Waveforms

Leading Anodal Biphasic (LABP)
Leading Cathodal Biphasic (LCBP
Anodal Monophasic (AMP)
Cathodal Monophasic (CMP)

Changes in Voltage Amplitude

2 to 8 Volts with 2 volt increments

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Results

Cathodal vs. Anodal Pacing

p < 0.05

Cathodal/Anodal Parameter	at 2 V	at 4 V	at 6 V	at 8 V
Pmax	1.02 (62 %)	0.97 (38 %)	0.97 (40 %)	0.93 (45 %)
P integral over one beat	0.98 (14 %)	0.96 (39 %)	0.98 (53 %)	0.89 (48 %)
dP/dt	0.98 (21 %)	0.97 (30 %)	0.97 (16 %)	0.95 (53 %)
Time delay Stim - Pmax	1.03 (31 %)	1.02 (45 %)	1.03 (56 %)	1.02 (62 %)

Conclusions

1) In this experimental model the anodal pacing pattern provided more efficient pacing through stronger mechanical response,

2) Further studies are required to establish the value of longer term anodal patterns in pacing hearts in-situ under different conditions, including ischemia, heart failure etc.

Future Plans:

Extremely long term pacing: implamentation of a pacemaker in an animal
Dual chamber pacing
To study change in overall heart function

Related papers:

1. Thakral, A., Stein, L., Shenai, M., Gramatikov, B.I. and Thakor, N.V. Effects of Anodal versus Cathodal Pacing on the Mechanical Performance of the Isolated Rabbit Heart. Journal of Applied Physiology, Vol. 89, Issue 3, 1159-1164, September 2000.

2. Thakral, A., Stein, L., Shenai, M., Gramatikov, B., Thakor, N. and Mower, M. Effects of varying the pacing waveform on mechanical performance in the rabbit heart. Pace, Vol.22, April 1999, Part II, p.750 (Abstracts of the 20th Annual Scientific Sessions of the North American Society of Pacing and Electrophysiology, NASPE, Toronto, May 12-15, 1999).

3. Thakral, A., Stein, L., Shenai, M., Gramatikov, B., Thakor, N. and Mower, M. Comparison of anodal vs. cathodal pacing patterns in isolated Langendorff perfused rabbit hearts. Abstracts of the Biomedical Engineering Society 1998 Annual Fall Meeting, 10-13 October 1998, Cleveland, OH. In Annals of Biomedical Engineering, Vol. 26, Suppl. 1, p. S-22, Abstract CB.46.

This page was created by Boris Gramatikov

Last update: November, 2000