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Cardiac performance early after cardioversion from atrial fibrillation
R J Raymond1, A J Lee, F C Messineo
1Cardiology Division of the University of Connecticut School of Medicine, Farmington, USA.
Insights
Cardioversion rapidly improves cardiac function by increasing stroke volume and ejection fraction. This enhancement is primarily due to better diastolic filling and restored atrial function, not changes in intrinsic contractility.
Area of Science:
- Cardiology
- Cardiac Electrophysiology
- Cardiovascular Physiology
Background:
- The precise mechanisms driving the immediate improvement in cardiac function following cardioversion from atrial fibrillation remain incompletely understood.
- Atrial fibrillation (AF) is a common arrhythmia affecting cardiac performance.
Purpose of the Study:
- To investigate the changes in ventricular volumes and load-independent cardiac contractility shortly after cardioversion from atrial fibrillation to normal sinus rhythm.
- To elucidate the underlying mechanisms responsible for early functional recovery post-cardioversion.
Main Methods:
- Ventricular volumes and load-independent contractility were assessed in 15 adult patients during atrial fibrillation and within 24 hours after successful cardioversion.
- Measurements included ejection fraction, stroke volume, mean cycle length, and cardiac contractility indices (Vcfc/ESWS).
Main Results:
- Left ventricular ejection fraction significantly increased from 51% to 61% (P=.001) and stroke volume rose from 57 mL to 76 mL (P < .001) post-cardioversion.
- Mean cardiac cycle length increased, indicating improved ventricular filling time.
- Intrinsic cardiac contractility (Vcfc/ESWS) remained largely unchanged in most patients, suggesting preserved inotropic state.
Conclusions:
- Immediate post-cardioversion increases in stroke volume and ejection fraction are observed.
- The primary drivers appear to be enhanced left ventricular diastolic filling, facilitated by increased cycle length and the restoration of left atrial mechanical function.
- Intrinsic contractility does not significantly change in the early period after restoring sinus rhythm.
Background:
The mechanism for early improvement in cardiac function after cardioversion from atrial fibrillation is unknown.
Methods:
We measured ventricular volumes and load-independent contractility during atrial fibrillation and within 24 hours after cardioversion to sinus rhythm in 15 adult patients (10 men, 5 women; mean age 63+/-4 years, range 31 to 81 years). Duration of atrial fibrillation ranged from <1 day to 6 months.
Results:
After cardioversion, left ventricular ejection fraction increased from 51%+/-4% to 61%+/-4% (P=.001, 95% confidence intervals for the difference, 7% to 15%), stroke volume increased from 57+/-4 mL to 76+/-6 mL (P < .001, 95% confidence intervals 8 to 32 mL), and mean cycle length increased from 0.77+/-.04 seconds in atrial fibrillation to 1.02+/-.04 seconds in sinus rhythm (P=.002, 95% confidence intervals, 0.1 to 0.4 seconds). Cardiac contractility, as expressed by the slope and the intercept of the relation between rate-corrected circumferential velocity of fiber shortening and end-systolic wall stress (Vcfc/ESWS) remained unaltered in 13 of 15 patients, suggesting that intrinsic inotropic state was unchanged immediately after return of normal sinus rhythm. Finally, a significant correlation was observed between improvement in stroke volume and peak A-wave velocity (r=0.79, P=.035).
Conclusion:
Both left ventricular stroke volume and ejection fraction increase immediately after cardioversion, whereas intrinsic cardiac contractility is largely unchanged. These data suggest that the mechanism of this increase is enhanced left ventricular diastolic filling due mostly to increased cycle length and return of left atrial mechanical function.