Jun 30 2004
Only recently was a type of diuretic known as thiazides been found to be superior to angiotensin-converting enzyme (ACE) inhibitors and calcium antagonists (calcium channel blockers) in preventing one or more major types of cardiovascular disease.
The diuretics also tend to have fewer and less severe side effects, making it easier to stay on medication. In addition, the diuretics are relatively inexpensive. Exercise has always been recommended for good cardiac health.
So what should the at-risk, older American do to sustain good cardiac health?
Hypertension or high blood pressure during the contraction of the heart is epidemic among older men and women. It is a major but modifiable risk factor for cardiovascular morbidity and mortality in old age. Left ventricular hypertrophy (LVH), or an enlarged heart, is commonly observed in a patient with hypertension and can be a powerful predictor of heart failure independent of level of blood pressure (BP) in hypertensive adults. Reduction of blood pressure during contraction can reduce the risk of stroke and heart failure in hypertensive older individuals. Furthermore, regression of LVH is likely to reduce cardiovascular risks in hypertension.
Endurance exercise training, which can include sustained walking, jogging or cycling, has been recommended for management of hypertension because it is effective in reducing blood pressure. Recent studies have shown that exercise training may also reduce left ventricular (LV) concentric remodeling and LVH. Since endurance exercise training improves increased levels of insulin in the plasma and insulin resistance it is possible that the benefits leading to increase in cardiac health may occur because insulin is a stimulus for the development of an enlarged heart. What is not clear is whether exercise can induce regression of LV remodeling in older adults or whether it is as effective as antihypertensive medications in reducing LV or enlarged cardiac mass in older hypertensive patients.
These were the issues addressed in a study that studied older adults with mild hypertension randomized into exercise and thiazide (diuretics that increase the excretion of sodium and chloride) groups to characterize (1) adaptive changes in LV mass, geometry, and function; and (2) the metabolic and hormonal changes in response to exercise training and to determine whether these adaptive responses were associated with alterations in LV mass, geometry and function.
The study’s authors speculated that endurance exercise training in older adults with mildhypertension could reduced blood pressure, relative LV wall thickness, heart enlargement, and hyperinsulinemia and that the effect of endurance exercise training on regression of LVH and LV remodeling is similar in magnitude to that induced by the thiazide diuretic.
The authors of “Comparison of the Effects of Exercise and Diuretic on Left Ventricular Geometry, Mass, and Insulin Resistance in Older Hypertensive Adults, are Morton R. Rinder, Robert J. Spina, Linda R. Peterson, Christopher J. Koenig, Christa R. Florence, and Ali A. Ehsani, all from the Washington University School of Medicine, St. Louis, MO. Their findings are published in the online edition of the American Journal of Physiology – Regulatory, Integrativ and Comparative Physiology. The journal is one of 14 published each month by the American Physiological Society (www.the-aps.org).
This study focused on the left ventricle relative wall thickness in addition to left ventricle mass because in hypertension LV remodeling appears to be as good or even better predictor of LV dysfunction and cardiac risk factor than LVH.
After an initial screening of 639 subjects, the researchers identified and recruited 51 eligible subjects with grade I and II hypertension who were older than 55 years, received no current treatment with antihypertensive medications, displayed an absence of symptomatic coronary artery and peripheral arterial diseases, and had no history of myocardial infarction or coronary artery bypass surgery, aortic aneurysm, significant valvular heart disease, congestive heart failure, or noncardiac chronic conditions that might interfere with exercise testing or training. Additionally the test subjects must not have used tobacco or had a sedentary lifestyle (defined as regular exercise less than one time a week) or geographical or job constraints that might prevent the them from regular participation in a supervised exercise training program.
After exclusions, 28 patients randomized either to a group (n = 16, age: 66.4 ± 1.3 yrs old) that exercised or to a group (n = 12, age: 65.3 ± 1.2 yrs old) that received hydrochlorothiazide for six months.
Endurance exercise training induced a 15% increase peak in aerobic power and consisted of increased time on a treadmill with increases in grade 2 percent every 2 minutes until exhaustion or development of symptoms or signs including ECG changes that were considered unsafe to continue. Blood pressure, cholesterol, plasma readings (volume and insulin) were administered.
The exercise endurance group participated in a five-month-long program; the test subjects receiving a thiazide diuretic received hydrochlorothiazide 25 to 50 mg daily with supplemental K+ 20 mEq daily for six months. The rationale for using thiazide was based on the recommendation by the Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure for older people with mild-to-moderate hypertension. Compliance with medication was verified by the “pill count.”
The findings revealed that endurance exercise training of mild-to-moderate intensity can induce a partial regression of LVH with reductions in LV mass index and relative wall thickness in older adults with mild hypertension. The data also suggests that the extent of this reversal is likely to be similar to that induced by thiazide diuretic.
Additionally, the researchers found that the reduction in systolic blood pressure with thiazide was greater than with exercise training. The regression of LVH in the volunteers is evidenced by reductions in the LV wall thickness-to-radius ratio, LV posterior and septal wall thicknesses without an increase in LV end-diastolic diameter or volume, and LV mass normalized for body surface area or fat-free mass. The absence of a significant change in LV end-diastolic diameter or volume suggests that the training stimulus was not sufficiently vigorous to induce superimposed volume-overload hypertrophy.
The findings of this study suggest that a program of mild-to-moderate intensity exercise training can result in partial regression of increased LV relative wall thickness and LVH that is similar to the effect induced by a thiazide diuretic. Although hydrochlorothiazide is considerably more effective in reducing systolic blood pressure than exercise, metabolic adaptations that occur only with exercise training can provide significant additional clinical benefits that are not attainable with a thiazide diuretic.
Therefore, endurance exercise training appears to be a suitable treatment strategy in some older adults with mild hypertension because despite a smaller decrease in blood pressure, it can induce a comparable regression of cardiac mass with improvements in insulin resistance and aerobic capacity and because aggressive reduction of blood pressure by antihypertensive medications may not necessarily confer a greater protection against the risk of death in hypertensive elderly patients.