Potassium depletion exacerbates essential hypertension

Article Abstract:

Essential hypertension is high blood pressure that has no obvious external cause. Left untreated, hypertension may result in kidney disease, arteriosclerosis, or other serious disorders. Epidemiological studies have shown that people with hypertension are more likely to have low intake of potassium. A diet low in potassium is also likely to be different from a high-potassium diet in many other ways. Therefore, it would invalid to assume that the low amounts of potassium contribute directly to the development of high blood pressure. To determine whether low potassium intake does, indeed, contribute directly to high blood pressure, 12 hypertensive, but otherwise healthy, subjects were given specially prepared meals in which only the potassium content was varied. The subjects ate standardized meals for five days, at which point they were switched to comparable meals low in potassium for the next 10 days. The sodium content of the meals was held constant throughout the experiment. At the end of 10 days, the blood pressure of the patients had increased. The average systolic (peak) blood pressure was 148 milliliters of mercury (mm Hg), in contrast with 141 mm Hg at the beginning of the low potassium diet. Similarly, the average diastolic blood pressure also rose to 96 mm Hg from 90 mm Hg. Blood and urine specimens taken during the course of the study indicated that the patients tended to retain sodium while on the low- potassium diet; at the same time, the excretion of calcium also rose. (A simultaneous increase in phosphorous excretion suggests that the calcium came from bone.) These changes may contribute to the elevation in blood pressure that occurs as body potassium is depleted. The details of the interactions between sodium, potassium, and calcium and their influence on blood pressure are not fully understood. (Consumer Summary produced by Reliance Medical Information, Inc.)

Potassium in the body, Potassium (Nutrient), Mineral metabolism, Water-electrolyte imbalances, Fluid-electrolyte imbalance, Essential hypertension, Potassium metabolism

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Contribution of external forces to left ventricular diastolic pressure: implications for the clinical use of the Starling law

Article Abstract:

Part of the diastolic pressure measured in the resting left ventricle of the heart appears to be due to forces outside the left ventricle. Of 29 patients who had heart catheterization, 12 had normal left ventricles and 12 had heart disease affecting the left ventricle. Researchers tested the effect of external forces on the left ventricle by blocking blood flow through the inferior vena cava for a brief period with a balloon catheter. This markedly reduced forces on the left ventricle from the right heart and the pericardium. Pressures within the ventricle were measured continuously before, during, and after blocking the inferior vena cava. Pressure declined an average of 19%, but cardiac output remained stable. Thirty to forty percent of the pressure inside the left ventricle was a result of external factors. The presence of heart disease had little effect on this.

Heart ventricle, Left, Left heart ventricle

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The Diastolic Blood Pressure in Systolic Hypertension

Article Abstract:

Some patients with high blood pressure only have systolic high blood pressure but not diastolic high blood pressure. During systole, the heart contracts and during diastole it fills with blood in preparation for the next contraction. The contraction of the heart during systole produces a wave of blood and the aorta normally expands to accommodate it. When the aorta becomes stiff it can no longer expand, and this causes systolic hypertension. However, diastolic blood pressure may be normal. It is best to treat such patients with a drug that will relax the aorta without lowering diastolic blood pressure too much.

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