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Heart and Vessels

, Volume 1, Issue 1, pp 9–15 | Cite as

Adaptations of the left ventricle to chronic volume overload induced by mitral regurgitation in conscious dogs

  • Jong Dae Lee
  • Shigetake Sasayama
  • Yasuki Kihara
  • Akira Ohyagi
  • Akiko Fujisawa
  • Yoshiki Yui
  • Chuichi Kawai
Originals

Summary

To assess the time-course of adaptive responses of the left ventricle to chronic volume overload, dogs were instrumented with a left ventricular (LV) micromanometer and pairs of ultrasonic crystals for the measurement of LV wall thickness (WTh), LV chamber diameter (D), and longitudinal segment length (L). Following a control study, mitral regurgitation (MR) was created by a transventricular section of the chordae tendineae. Heart rate was controlled during each study by atrial pacing. Plasma norepinephrine levels at rest were determined by high-performance liquid chromatography. Eight days (mean) after the onset of MR, end-diastolic (ED) D had increased by 9% from 34.2±2.4 mm (SEM) (P<0.001), wit significant thinning of the wall thickness (from 8.2 to 7.7 mm,P<0.001). Consequently the calculated cross-sectional area (CSA) of the left ventricular wall remained the same. Peak wall stress (WSt) and EDWSt increased by 20% and 152%, respectively. During the subsequent 4 weeks, EDD progressively increased, averaging 11% above the control at 4 weeks, while EDWTh returned to the control level. Thus, the development of hypertrophy was clearly evidenced by an increase in CSA (by 8% over the control,P<0.001). These changes were accompanied by a consistent reduction in both peak WSt and EDWSt. Mean velocity of circumferential fiber shortening (meanVcf) and percentage shortening were significantly augmented following the onset of MR and remained at the same level thereafter, indicating no further use of the Frank-Starling mechanisms during chronic ventricular dilation. Despite a progressive increase in diameter, longitudinal segment length did not increase throughout the study, suggesting that the ventricle assumes a more globular appearance, as an additional compensatory mechanism to prevent excessive enhancement of diastolic wall stress, Initially elevated plasma norepinephrine concentrations (from 127±28 to 256±69 pg/ml,P<0.05) tended to decrease with the development of hypertrophy (202±55 pg/ml). These data support the view that hypertrophy and change in shape of the left ventricle take place during the course of chronic adaptation to volume overload and normalize the elevated wall stress as a negative feedback. Along with the decrease in wall stress, the initially enhanced sympathetic activity decreases gradually during adaptation to chronic volume overload.

Key words

Chronic volume overload Mitral regurgitation Left ventricular hypertrophy Sympathetic activity 

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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Jong Dae Lee
    • 1
  • Shigetake Sasayama
    • 1
  • Yasuki Kihara
    • 1
  • Akira Ohyagi
    • 1
  • Akiko Fujisawa
    • 1
  • Yoshiki Yui
    • 1
  • Chuichi Kawai
    • 1
  1. 1.The Third Division, Department of Internal Medicine, Faculty of MedicineKyoto UniversityKyotoJapan

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