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Serial effects on left ventricular load and contractility during hemodialysis in patients with concentric hypertrophy
Insights
Hemodialysis reduces heart size and improves shortening in patients with left ventricular hypertrophy. These changes are primarily due to decreased preload and afterload, not altered contractile state.
Area of Science:
- Cardiology
- Nephrology
- Physiology
Background:
- Left ventricular hypertrophy (LVH) can alter cardiac loading conditions and contractile function.
- Hemodialysis (HD) significantly impacts fluid and electrolyte balance, affecting cardiovascular hemodynamics.
Purpose of the Study:
- To differentiate the effects of hemodialysis on loading conditions versus contractile state in patients with LVH.
- To investigate the impact of hemodialysis on left ventricular dimensions, stress, and shortening.
Main Methods:
- Studied six patients with LVH before, during, and after hemodialysis.
- Utilized 2D-guided M-mode ultrasound for left ventricular measurements.
- Measured blood pressure, calculated end-systolic meridional stress, and derived stress-dimension/stress-shortening relations.
Main Results:
- Hemodialysis led to reduced left ventricular dimensions and increased shortening, evident within 30 minutes.
- These changes correlated with decreased potassium and increased ionized calcium, while pH remained stable initially.
- Analysis of stress-dimension and stress-shortening relations indicated a consistent contractile state throughout dialysis.
Conclusions:
- In stable LVH patients, hemodialysis-induced reductions in heart size and improved shortening are mainly attributed to decreased preload and afterload.
- The contractile state of the left ventricle remains largely unchanged during hemodialysis in this population.
Abstract:
To separate the effects of hemodialysis on loading conditions from those on contractile state, six patients with concentric left ventricular hypertrophy and normal left ventricular function were studied before, during, and after hemodialysis. Two-dimensional-directed M-mode ultrasound was used to measure left ventricular dimensions and wall thickness; a sphygmomanometer and carotid pulse recording were used to determine peak and end-systolic blood pressure. From these data, meridional stress at end systole was calculated and stress-dimension and stress-shortening relations were derived; measurements of metabolic parameters were made simultaneously. Heart rate and systolic blood pressure were stable throughout dialysis. Reductions in left ventricular dimensions and increased shortening were evident by 30 minutes of dialysis and were largely complete by mid-dialysis. These changes coincided with a decrease in potassium and an increase in ionized calcium but not in pH, which changed only in the latter half of dialysis. When stress-dimension and stress-shortening relations were examined, both individual and group data for all coordinates before, during, and after dialysis demonstrated an excellent linear fit consistent with a single contractile state. We conclude that in stable patients with left ventricular hypertrophy, the reduction in heart size and improvement in shortening are due primarily to reductions in preload and afterload.