Left Ventricular Mechanics and Myocardial Blood Flow: Statistical Analysis

Left Ventricular Mechanics and Myocardial Blood Flow: Statistical AnalysisAll measurements in these arteries were recorded during DDD and AAI pacing modes.
Continuous variables are summarized as the mean ± SD. Changes in the various parameters between DDD and AAI pacing modes were assessed with the t test for dependent samples and the Wilcoxon signed rank test. Both parametric and nonparametric tests gave significant results for the same parameters. The level of significance was set at 5%.
From an initial pool of 2,360 paced patients, 22 fulfilled the inclusion criteria and consented to participate in the study. In six patients, the conductance catheter signals were not satisfactory during off-line analysis, and they were all excluded. The recordings in four patients included too many extrasystoles, and the recordings were unacceptable in the remaining two patients as a result of noise due to catheter position. Finally, 16 patients (9 men; mean age, 61 ± 11 years) with a mean pacing duration of 39 ± 8 months were considered for analysis.
We examined the alterations in LV mechanics in eight patients (five men; mean age, 59 ± 10 years) and the changes in coronary flow in the remaining eight patients (four men; mean age, 63 ± 12 years) using a conductance catheter with a micromanometer on the tip and a Doppler guidewire, respectively. Patients in the LV mechanics group (group 1) and the coronary flow measurements group (group 2) had similar clinical characteristics (Table 1). canadian family pharmacy

LV Systolic Performance
After restoration of a normal ventricular activation sequence, the Ees increased significantly (4.287 ± 0.28 mm Hg/mL vs 5.503 ± 0.59 mm Hg/mL, respectively; p = 0.003), suggesting that intrinsic myocardial contractility was enhanced (Fig 1). Similarly, LVEF (46 ± 4.7% vs 49 ± 4.7%, respectively; p = 0.002), PRSW (91.78 ± 6.14 mm Hg vs 100.99 ± 12.32 mm Hg, respectively; p = 0.033), and the ventriculaorterial coupling index Ees/Ea (1.63 ± 0.51 vs 2.00 ± 0.64, respectively; p = 0.009) also increased significantly.
Figure 1. LV pressure-volume loops from a patient during baseline DDD pacing mode (top, A) and after switching to AAI pacing mode (bottom, B). There was negligible effect on Pes and end-diastolic pressure or Ves and Ved from switching the pacing mode. However, the LV Pes-Ves relationship slope (ie, the Ees) increased significantly after the restoration of a normal ventricular activation sequence.
Table 1—Patient Characteristics

Characteristics Group 1 Group 2 p Value
Age, yrt (mean ± SD) 59 ± 10 63 ± 12 0.416
Male 5 4 NS
Female 3 4
Arterial hypertension 4 5 0.370
Diabetes mellitus 0 1 0.211
Cigarette smoking 3 3 0.814
Paroxysmal atrial fibrillation 4 3 0.353
ACE inhibitors 4 5 0.419
P-blockers 4 5 0.530
Calcium channel blockers 2 1 0.174
Propafenone 4 3 0.299