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Cardiac function in sickle cell anemia
Insights
Sickle cell anemia (SCA) patients show depressed left ventricular (LV) muscle function, masked by increased preload and decreased afterload. These compensatory mechanisms maintain normal ejection fraction and cardiac output despite underlying LV dysfunction.
Area of Science:
- Cardiology
- Hematology
- Physiology
Background:
- Congestive heart failure is suspected in sickle cell anemia (SCA), but ejection indexes of left ventricular (LV) pump performance are often normal.
- Increased preload and decreased afterload in SCA can mask true LV dysfunction by artificially inflating ejection phase indexes.
Purpose of the Study:
- To compare the preload and afterload independent end-systolic stress-volume index in patients with SCA and healthy volunteers.
- To investigate underlying left ventricular (LV) contractile performance in SCA, independent of preload and afterload variations.
Main Methods:
- Echocardiographic LV dimensions and end-systolic pressure were measured in 11 SCA patients and 11 controls.
- Measurements were taken at rest and during interventions including leg raise, hand-grip, and amyl nitrite inhalation.
- Systemic vascular resistance (afterload) and end-diastolic volume index (preload) were calculated.
Main Results:
- SCA patients had significantly decreased afterload and increased preload compared to controls.
- Despite similar ejection fractions, SCA patients exhibited a decreased end-systolic stress-volume index ratio and slope.
- Cardiac index was elevated in SCA patients.
Conclusions:
- Left ventricular (LV) muscle contractile performance is depressed in patients with sickle cell anemia (SCA).
- Compensatory increases in preload and decreases in afterload maintain normal ejection fraction and cardiac output in SCA.
- The end-systolic stress-volume index is a valuable tool for detecting subclinical LV dysfunction in SCA.
Abstract:
Although ventricular dysfunction is suspected to underlie congestive heart failure in sickle cell anemia (SCA), ejection indexes of left ventricular (LV) pump performance have been found to be normal. The increased preload and decreased afterload of SCA increases the ejection phase indexes and might obscure true LV dysfunction. Therefore, the preload and afterload independent end-systolic stress-volume index was compared in 11 patients with SCA and in 11 normal volunteers. End-systolic pressure and echocardiographic LV dimensions were determined during rest, leg raise, hand-grip and amyl nitrite inhalation. Systemic vascular resistance (afterload) was decreased to 1,033 +/- 314 dynes s cm-5 (mean +/- standard deviation) in SCA from 1,701 +/- 314 dynes s cm-5 in normal subjects. End-diastolic volume index (preload) was increased to 102 +/- 24 ml/m2 in SCA from 66 +/- 10 ml/m2 in normal subjects. Cardiac index was increased to 4.7 +/- 1.1 liters/min/m2 in SCA from 2.8 +/- 0.8 liters/min/m2 in normal subjects. Ejection fractions were similar: 0.59 +/- 0.09 in SCA versus 0.62 +/- 0.07 in normal subjects. However, in patients with SCA, the ratio of resting end-systolic stress-volume index was decreased (1.5 +/- 0.5 in SCA versus 2.8 +/- 0.6 in normal subjects) and the slope of the end-systolic stress versus end-systolic volume index relation was decreased (2.7 +/- 1.3 in SCA versus 4.4 +/- 1.8 in normal subjects), suggesting LV dysfunction in those patients. Thus, LV muscle contractile performance is depressed in SCA. Increased preload and decreased afterload compensate for the LV dysfunction and maintain a normal ejection fraction and high cardiac output.