Clinical Investigations: Acute Ischemic Heart Disease
Left ventricular function in atrial fibrillation during overdrive pacing*,**,★

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Abstract

Objective Our purpose was to measure the effect of ventricular pacing in patients with atrial fibrillation (AF) on stroke volume and cardiac output. Background Unceasing variation in cycle length in AF decreases stroke volume and cardiac output. Because ventricular-inhibited pacing after atrioventricular node ablation has been reported to improve left ventricular performance, we tested the hypothesis that overdrive pacing would produce a similar benefit by regularizing cycle length. Methods and Results We studied 18 patients with chronic AF and permanent pacemakers. The aortic time velocity integral (TVI) was measured with continuous-wave Doppler and was used as a surrogate measure of stroke volume (stroke volume = TVI × aortic valve area, and aortic valve area is constant whether in AF or during pacing). For each patient, the linear relation between preceding cycle length and TVI in AF was used to estimate relative stroke volume (TVI compared within each patient) at a preceding cycle length of 666 ms in AF, and a similar comparison between AF and pacing was made at the minimum allowable pacing rate. Relative stroke volume in AF was then compared with relative stroke volume at both the fixed cycle (666 ms) and the minimum allowable rate. During pacing at 666 ms, relative stroke volume increased significantly by 18% (t = 2.8, P =.048), but there was no difference in cardiac output during pacing at the minimum possible rate and the corresponding preceding cycle length in AF. Conclusion Our data suggest that regularization of ventricular rhythm by overdrive pacing in patients with AF only improves stroke volume (and by extension, cardiac output) at pacing rates at the outer limit of and above the normal physiologic range. (Am Heart J 2002;143:827-32.)

Section snippets

Study protocol

Eighteen patients with previously placed permanent ventricular pacemakers and documented chronic AF were recruited from the John Dempsey and Grove Hill Cardiology pacemaker services. Patients with left bundle branch block at baseline were excluded from the study. All pacemaker leads were placed within the right ventricular apex. Standard 2-dimensional echocardiography was performed with a Hewlett-Packard Sonos 2500 echocardiograph (Palo Alto, Calif). Left atrial size was estimated with standard

Results

The clinical characteristics and baseline echocardiographic measurements for each patient are presented in Table I.

. Patient characteristics

PatientAgeSexAF etiologyMedicationsLA size (cm)LV Fn
174FHTND4.0↓ ↓
274MHTNA,C,D4.5↓ ↓
382MHTN, CADA,B,D5.5↓ ↓
472MHTNC,ARB4.6↓ ↓
590MHTNA,D4.0↓
690MHTN, CADA,D,G4.0↓ ↓
775MHTN, CADB3.9↓ ↓
885MHTNA,C4.0Normal
982FHTNA,D,G4.6↓ ↓
1089MHTN, CADA,B,D4.5Normal
1176MHTN4.5Normal
1273MHTN, CADA,B,C,D4.3Normal
1340MHTNC,D4.4↓
1483FHTNC,D4.1↓
1573FHTNB,G3.4Normal
1695FHTNA,C,D5.0↓
1774

Discussion

We observed 3 differences between cardiac performance during AF and overdrive pacing. First, stroke volume, as estimated by TVI, is greater during cardiac pacing than AF at the same cycle length (Figure 1). Second, the difference between TVI during AF and pacing narrows as cycle length increases. Third, decreasing cycle length during pacing does not increase TVI, regardless of baseline left ventricular function. These data agree with previous studies that report that cardiac output is increased

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    *

    Supported in part by National Institutes of Health General Clinical Research Center Grant No. MO1RR06192, and a grant from the Claude Pepper Center for Older Americans, No. 5P60-AG13631-03 (D.I.S.).

    **

    Reprint requests: David I. Silverman, MD, Cardiology, University of Connecticut Health Center, 263 Farmington Ave, Farmington, CT 06030-1305.

    ★

    E-mail: [email protected]

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