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Relationship between beat-to-beat changes in hemodynamic state and action potential duration of the left ventricle
H V Huikuri1, K J Peuhkurinen, J T Takkunen
1Department of Medicine, Oulu University Central Hospital, Finland.
Insights
This study reveals an immediate force-interval relationship in the human left ventricle. Beat-to-beat variations in blood pressure directly correlate with changes in action potential duration (APD), impacting cardiac function.
Area of Science:
- Cardiology
- Electrophysiology
- Hemodynamics
Background:
- Understanding the interplay between cardiac electrical activity and mechanical function is crucial for cardiovascular health.
- Beat-to-beat variability in hemodynamic parameters can reflect underlying cardiac regulatory mechanisms.
- Action potential duration (APD) is a key determinant of cardiac repolarization and refractoriness.
Purpose of the Study:
- To investigate the relationship between beat-to-beat changes in hemodynamic state and left ventricular action potential duration (APD).
- To determine if an immediate force-interval relationship exists in the human left ventricle.
Main Methods:
- Right ventricular pacing at a constant cycle length (400 msec) for 3 minutes in 16 patients.
- Simultaneous recording of intra-arterial pressure and left ventricular monophasic action potential (MAP).
- Analysis of beat-to-beat variations in APD (measured at 90% repolarization, APD-90) and blood pressure.
Main Results:
- Left ventricular APD-90 shortened significantly during pacing, reaching a minimum after approximately 160 seconds.
- Beat-to-beat variation in APD was directly correlated with variation in mean arterial blood pressure (r = 0.65, P < 0.01).
- An increase in blood pressure of 10 mmHg was associated with an APD increase of at least 5 msec.
- Sequential ventriculoatrial pacing reduced beat-to-beat variations in both APD and blood pressure in patients with ventriculoatrial dissociation.
Conclusions:
- An immediate force-interval relationship exists in the human left ventricle.
- Beat-to-beat hemodynamic changes directly influence left ventricular electrical state (APD).
- These findings have implications for understanding cardiac dynamics and potential therapeutic interventions.
Abstract:
A relationship between beat-to-beat changes in hemodynamic state and action potential duration (APD) of the left ventricle was studied by pacing the right ventricle with a constant cycle length (400 msec) for 3 minutes and recording simultaneously the intraarterial pressure and left ventricular monophasic action potential in 16 patients (mean age 51 +/- 8 years) undergoing routine cardiac catheterization. The APD measured at the point of 90% repolarization (APD-90) shortened gradually from a baseline value of 305 +/- 25 msec to a minimum of 246 +/- 25 msec (P less than 0.001) by 160 +/- 10 seconds after the onset of pacing. After reaching the minimum duration, the APD and blood pressure were measured from 30 consecutive beats. The magnitude of beat-to-beat variation in the APD was directly correlated to variation in the mean arterial blood pressure (r = 0.65, P less than 0.01). Beat-to-beat changes in hemodynamic and electrical state were related in that an increase of at least 10 mmHg in the blood pressure of one beat was associated with an increase in the APD of the concomitant beat by at least 5 msec. In six patients with ventriculoatrial dissociation during the rapid ventricular pacing, the sequential ventriculoatrial pacing decreased the beat-to-beat variation of APD from 2.8% +/- 1.4% to 0.8% +/- 0.7% (P less than 0.01) and variation of blood pressure from 6.4% +/- 3.2% to 1.4% +/- 0.9% (P less than 0.01). The observed association between beat-to-beat changes in hemodynamic state and APD of the left ventricle demonstrates that an immediate force-interval relationship exists in the human left ventricle.