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Tachycardia-induced cardiomyopathy: effects on blood flow and capillary structure
F G Spinale1, J L Zellner, M Tomita
1Division of Cardiothoracic Surgery, Medical University of South Carolina, Charleston 29425.
Insights
Chronic supraventricular tachycardia (SVT) impairs myocardial blood flow (MBF) and left ventricular (LV) function, leading to cardiomyopathy. This study reveals reduced MBF in SVT pigs, contributing to cardiac dysfunction.
Area of Science:
- Cardiology
- Physiology
- Pathology
Background:
- Chronic supraventricular tachycardia (SVT) is linked to dilated cardiomyopathy.
- Abnormal myocardial blood flow (MBF) is a suspected contributor to SVT-induced cardiomyopathy.
Purpose of the Study:
- To investigate the relationship between left ventricular (LV) function, MBF, and capillary structure in the development of SVT-induced cardiomyopathy.
- To compare these parameters between control and SVT pigs under various physiological conditions.
Main Methods:
- Conscious pigs underwent 3 weeks of atrial pacing (SVT group) or sham control (CON group).
- LV function and MBF were assessed using echocardiography-catheterization and microspheres at rest, during pacing, and with adenosine infusion.
- LV capillary density, diameter, wall thickness, and capillary-myocyte distance were measured post-mortem.
Main Results:
- SVT pigs exhibited lower LV fractional shortening and higher left atrial pressure compared to CON pigs across all tested states.
- Myocardial blood flow (MBF) was significantly reduced in SVT pigs at rest, during pacing, and with adenosine infusion compared to CON pigs.
- While MBF increased with pacing and adenosine in CON pigs, it remained significantly blunted in SVT pigs.
Conclusions:
- Reduced myocardial blood flow (MBF) is a significant factor in the development of left ventricular dysfunction during chronic supraventricular tachycardia (SVT).
- SVT-induced changes in cardiac structure and function, including impaired MBF, contribute to the pathogenesis of cardiomyopathy.
Abstract:
Chronic supraventricular tachycardia (SVT) causes a dilated cardiomyopathy. A potential factor contributing to the development of SVT-induced cardiomyopathy is abnormal myocardial blood flow (MBF). The purpose of this study was to relate changes in left ventricular (LV) function, MBF, and capillary structure with the development of SVT-induced cardiomyopathy. LV function and MBF were measured in two groups of conscious pigs: sham control (CON; n = 8) and after 3 wk of atrial pacing (SVT; 240 beats/min; n = 8) using echocardiography-catheterization and microspheres. Measurements were made under three states: 1) at rest with a basal heart rate, 2) during rapid atrial pacing (240 beats/min), and 3) during adenosine infusion (1.5 microM.kg-1.min-1) without pacing. LV capillary density, diameter, wall thickness, and capillary-myocyte distance were measured in four additional pigs from each group. LV fractional shortening was lower, and left atrial pressure was significantly higher in the SVT group compared with CON at rest, during pacing, and with adenosine (P less than 0.05). In the CON group, average LV-MBF at rest was 2.0 +/- 0.2 ml.min-1.g-1, increased with pacing to 3.0 +/- 0.2 ml.min-1.g-1 (P less than 0.05), and increased further with adenosine to 4.1 +/- 0.3 ml.min-1.g-1 (P less than 0.05). In all states, SVT LV-MBF was significantly reduced vs. CON (P less than 0.05); SVT LV-MBF was 0.8 +/- 0.2 ml.min-1.g-1 at rest, increased to 1.3 +/- 0.3 ml.min-1.g-1 with rapid pacing (P less than 0.05), and remained unchanged during adenosine (1.3 +/- 0.4 ml.min-1.g-1).(ABSTRACT TRUNCATED AT 250 WORDS)