Further insights into blood pressure induced premature beats: Transient depolarizations are associated with fast myocardial deformation upon pressure decline

Heart Rhythm. 2015 Nov;12(11):2305-15. doi: 10.1016/j.hrthm.2015.06.037. Epub 2015 Jun 30.

Abstract

Background: An acute increase in blood pressure is associated with the occurrence of premature ventricular complexes (PVCs).

Objective: We aimed to study the timing of these PVCs with respect to afterload-induced changes in myocardial deformation in a controlled, preclinically relevant, novel closed-chest pig model.

Methods: An acute left ventricular (LV) afterload challenge was induced by partial balloon inflation in the descending aorta, lasting 5-10 heartbeats (8 pigs; 396 inflations).

Results: Balloon inflation enhanced the reflected wave (augmentation index 30% ± 8% vs 59% ± 6%; P < .001), increasing systolic central blood pressure by 35% ± 4%. This challenge resulted in a more abrupt LV pressure decline, which was delayed beyond ventricular repolarization (rate of pressure decline 0.16 ± 0.01 mm Hg/s vs 0.27 ± 0.04 mm Hg/ms; P < .001 and interval T-wave to peak pressure 1 ± 12 ms vs 36 ± 9 ms; P = .008), during which the velocity of myocardial shortening at the basal septum increased abruptly (ie, postsystolic shortening) (peak strain rate -0.6 ± 0.5 s(-1) vs -2.5 ± 0.8 s(-1); P < .001). It is exactly at this time of LV pressure decline, with increased postsystolic shortening, and not at peak pressure, that PVCs occur (22% of inflations). These PVCs preferentially occurred at the basal and apical segments. In the same regions, monophasic action potentials demonstrated the appearance of delayed afterdepolarization-like transient depolarizations as origin of PVCs.

Conclusion: An acute blood pressure increase results in a more abrupt LV pressure decline, which is delayed after ventricular repolarization. This has a profound effect on myocardial mechanics with enhanced postsystolic shortening. Coincidence with induced transient depolarizations and PVCs provides support for the mechanoelectrical origin of pressure-induced premature beats.

Keywords: Blood pressure; Mechanoelectrical coupling; Postsystolic shortening; Premature ventricular complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Body Surface Potential Mapping*
  • Cardiac Complexes, Premature / diagnosis
  • Cardiac Complexes, Premature / etiology
  • Disease Models, Animal
  • Echocardiography, Doppler
  • Female
  • Heart Rate / physiology
  • Hypertension / complications*
  • Male
  • Mechanoreceptors / physiology
  • Myocardial Contraction / physiology*
  • Pressure
  • Random Allocation
  • Sensitivity and Specificity
  • Sus scrofa
  • Systole / physiology
  • Ventricular Function, Left / physiology*
  • Ventricular Premature Complexes / diagnosis
  • Ventricular Premature Complexes / etiology*