BEAT-TO-BEAT ANALYSIS OF LEFT-VENTRICULAR PRESSURE-VOLUME RELATION AND STROKE VOLUME BY CONDUCTANCE CATHETER AND AORTIC MODELFLOW IN CARDIOMYOPLASTY PATIENTS
Jj. Schreuder et al., BEAT-TO-BEAT ANALYSIS OF LEFT-VENTRICULAR PRESSURE-VOLUME RELATION AND STROKE VOLUME BY CONDUCTANCE CATHETER AND AORTIC MODELFLOW IN CARDIOMYOPLASTY PATIENTS, Circulation, 91(7), 1995, pp. 2010-2017
Background Since the clinical introduction of dynamic cardiomyoplasty,
a discrepancy has been observed between unchanged measurements of car
diac function and improved clinical outcome. Methods and Results We pe
rformed a beat-to-beat analysis of cardiac performance at rest in nine
cardiomyoplasty patients 6 to 24 months after operation. Conductance
and micromanometer catheters were placed in left ventricle and aorta a
nd used for measurements over a 15-second period, during which the wra
pped latissimus dorsi (LD) muscle was stimulated for 10 seconds in a 1
:2 synchronization mode followed by a 5-second period without LD stimu
lation. The synchronization delay between start of the QRS complex and
the LD contraction was changed from 3 up to 125 ms at the patient's c
linical stimulation strength and at an increased supramaximal amplitud
e. Comparing the LD assisted period to the unassisted period, at the c
linical settings no significant changes in stroke volume (SV) as measu
red by the conductance technique and the aortic Modelflow technique we
re observed. A significant (P<.05) rise in left ventricular end-diasto
lic pressure (LVEDP) was observed directly after the assisted 10-secon
d period. The peak ejection rate (PER) of left ventricular volume incr
eased (P<.05), with a mean of 28+/-23% during the LD stimulated beats.
At the patient's individual best setting, SV of the stimulated beats
increased (P<.01) by a mean of 20+/-15%. Systolic aortic pressure incr
eased (P<.01) by a mean of 7 mm Hg, peak negative dP/dt increased (P<.
01), and PER increased, with a mean of 68+/-24% (P<.01). LVEDP was sim
ilar in stimulated and unstimulated beats and increased (P<.05) in the
nonpaced 5-second period. The delay for the best setting ranged from
25 to 125 ms; the stimulus strength was 1.5 to 3 V higher than the cli
nical setting. At the patient's individual worst setting, SV remained
unchanged and PER was higher, with a mean of 30+/-25% (P<.05). The wor
st setting was observed at the 1.5- to 3-V-higher stimulus strength; i
n six patients, it was at a short delay (4 to 25 ms) and in three pati
ents, at the longest delay (100 to 125 ms). Conclusions By the left ve
ntricular conductance catheter and aortic Modelflow methods, improveme
nt in cardiac function by dynamic cardiomyoplasty was demonstrated in
this patient group. The synchronization interval, stimulus strength, a
nd stimulus duration appeared to be critical for obtaining optimal imp
rovement.