Gherardo Gherarducci, Stefano
Viani, Paolo Caravelli, Flavio Buttitta, Alberto Balbarini, Mario Mariani.
Cardiovascular and Pulmonary Department, University of Pisa, Italy
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Our patient population consisted of 21 patients (16
males and 5 females; mean age 70 ± 6; range 59-83) consecutively implanted at our
institution because of symptomatic conduction disease: complete heart block in 11 patients
(52%), II degree type 2 heart block in the other 10 patients (48%). The associated heart
diseases were: surgically corrected aortic valve stenosis in 9 patients (43%), coronary
artery disease in 2 patients (9%), systemic arterial hypertension in 4 patients (19%),
dilated cardiomyopathy in 1 patient (5%); no anamnestic, clinical or instrumental evidence
of any heart disease was found in the other 5 patients (24%). All the patients were
implanted with a single lead VDD pacing system (Intermedics Unity 292-07) because of a
normal sinus node function assessed by atropine test. Hemodynamic conditions were stable
in all the patients at the moment of evaluation that was performed 20 ± 2 days after
pacemaker implantation.
In each patient we measured, in the supine position during post-expiratory apnea after
a 15' rest period, the time-velocity integral of common carotid artery flow (TVI-CCA: cm)
digitazing the envelope around the velocity-time spectrum obtained by the Doppler
technique combined with 2-dimensional echography (Hewlett-Packard Sonos 2000 - 7.5 Mhz
probe). We averaged 5 consecutive cardiac cycles in VDD and 10 consecutive cycles in VVI
pacing mode. In the former pacing mode the atrioventricular interval was set at 75, 100,
150 (nominal setting), 200 and 250 ms in random succession, after a 5' adaptation period,
in VVI pacing mode stimulation rate was set 3 beats/min over the rest sinus rate in order
to obtain a totally paced rhythm. Continuous ECG monitoring confirmed that ventricular
contractions, both in VDD and in VVI mode, were completely induced by a pacemaker
stimulus. We defined the: 1. "optimal" atrioventricular delay (HF-AV) associated
with the highest value of time-velocity integral; 2. "worst" atrioventricular
delay (LF-AV) associated with the lowest value of velocity-time integral. Blood pressure
and heart rate were recorded at each atrioventricular interval in VDD pacing and during
VVI stimulation. The time-velocity integral of diastolic mitral flow (TVI-MC:\WWW cm)
expression of left ventricular filling volume, was determined at the same time and by the
same technique, at each atrioventricular interval and during VVI pacing. Use of the
time-velocity integrals allows comparison of relative changes in carotid flow and left
ventricular filling volume in individual patients without introducing potential errors of
measurement of the cross-sectional area of the common carotid artery or the mitral
annulus. One week after the assessment of the optimal atrioventricular delay every patient
performed an ergospirometric test on tread-mill (Medi-Soft Belgium Partn'Air 5400 system)
in order to assess oxygen consumption (VO2: ml/kg/min) and exercise duration
(Ex dur: sec) during VDD and VVIR pacing mode.
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