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Elevated blood pressure (BP) is a common finding in arterial hypertension and exercise. Similar as well as Differing hemodynamic changes may affect the circulatory system in these two conditions and may lead to “target” organ damage. Reviewing the hemodynamic changes in exercise and hypertension as to their similarities and differences may lead to better understanding their effect on the systemic circulation.

Hemodynamic changes are different in the two types of physical exercise. In isotonic exercise (endurance, aerobic, or dynamic), systolic arterial pressure and heart rate are markedly increased. Diastolic pressure remains unchanged or is slightly reduced and pulse pressure is increased. Mean arterial pressure shows little change or is moderately increased. Stroke volume, cardiac output, coronary arterial flow, and coronary flow reserve are increased.[1] Overall, the left ventricle faces a volume overload with lowered peripheral resistance. With intensive and sustained exercise, as in athletes, left ventricular dimensions and myocardial thickness are increased, leading to eccentric hypertrophy.[2] Left atrial diameter may also be increased. In the long run, exercise may reduce daytime but not nighttime pressure.[3]

In isometric exercise (resistance, anaerobic, strength, or static), systolic, diastolic, and mean arterial pressure are markedly elevated. Stroke volume is lowered or unchanged and cardiac output and heart rate are slightly increased. Coronary arterial flow and coronary flow reserve are also increased.[4] Peripheral resistance is increased in the exercised muscles but not in others. Overall, the left ventricle faces a pressure load or, in some kinds of exercise, a combined pressure and volume load.[5] Left atrial diameter was found to be increased. Left ventricular diameter was found to be increased but moderately in competitive athletes and does not exceed 13 mm in myocardial thickness.[4, 6]

Metabolic effects do not differ between the two types of exercise: insulin sensitivity is increased, triglycerides are lowered, and high-density lipoprotein is increased.[7]

In arterial hypertension, systolic and, in a number of cases, diastolic arterial pressure is increased. Pressure variability is expressed as night nondipping, morning pressure surge, 24-hour velocity and acceleration changes, and time rate changes, resulting in left ventricular mass changes. They may occur even with systolic and diastolic pressure in the “normal” range.[8] Heart rate may be normal or slightly elevated. Pulse pressure is increased, more so in elderly individuals. Mean arterial pressure may be elevated and stroke volume is reduced. Cardiac output is normal in the majority of patients and may be reduced at the beginning or at the end of hypertensive heart disease.[1] Stroke work is increased. Left ventricular hypertrophy is found in 20% to 30% of individuals with mild to moderate hypertension and in 50% to 60% of all hypertensive patients. Nighttime systolic and diastolic BPs are more closely correlated with left ventricular mass index than daytime values.[9] Coronary arterial flow is increased but coronary flow reserve may be impaired. The left ventricle experiences a pressure load with increased peripheral resistance, which, in advanced stages, may lead to remodeling of peripheral arteries. Interstitial fibrosis in the myocardium is also observed.[10] Lower than normal (by current standards) pressure values may affect the function of peripheral organs (heart, brain, kidneys) by reducing blood flow below the minimal requirements. Mortality caused by myocardial infarction is found to increase with low pressure, and the existence of a J curve is recognized[11, 12] more so for myocardial infarction than for stroke.

Ιn many cases of arterial hypertension and in intensive exercise of both types, some hemodynamic parameters such as systolic arterial pressure, heart rate, pulse pressure, and coronary flow are found to change in the same direction. Further similarities are found between hypertension and intensive isometric exercise concerning diastolic and mean 24-hour arterial pressure, and stroke volume.

The main difference between hypertension and exercise lies in peripheral resistance, which decreases in isotonic exercise and increases in hypertension and only in the exercised muscles in isometric exercise. Another important difference is found in the percentage of “abnormal” pressure values in a 24-hour period. Elevated pressure values appear during the time of exercise, which is usually limited but may be sustained as in competitive athletes. In mild hypertensive patients, 43 (53±28, 71%) of the 24-hour systolic pressure values were over 140 mm Hg and 31 (53±24, 75%) of diastolic pressure values were over 90 mm Hg vs 12 (83±10, 17%) and 10 (23±7, 93%) in normotensives.[13] Thus, elevated BP may be an intermittent or sustained stimulus for target organ damage in hypertensive patients and in competitive athletes. Cardiac output is increased during exercise, more markedly in isotonic exercise, but not in hypertensive patients. Coronary flow reserve is also unchanged or reduced in hypertensive patients but is increased during exercise. These hemodynamic differences and similarities between hypertension and the two types of exercise affect the left ventricle and the coronary circulation.

Well-known benefits of properly applied exercise include better-regulated lipids and glucose metabolism, better adaptation to stress, and improvement of body weight. Hypertension on the other side is a disease inflicting target organ damage to the left ventricle, the coronary circulation, carotid and other peripheral arteries, especially cerebral and renal. However, a certain level of BP, systolic or mean, seems to be necessary to maintain adequate flow to vital organs, more so in elderly individuals with coexisting atherosclerosis. The latest European Society of Cardiology/European Society of Hypertension guidelines have indicated a systolic pressure of 140 mm Hg as the treatment target for hypertensive patents except in very specific cases.[14]

The common characteristic of hypertension and exercise, the elevated BP and resulting changes in some hemodynamic parameters that affect vital organs, may be similar in cases of sustained exercise (especially isometric) in healthy individuals and in mild hypertension. The level of pressure and the length of time during which it is elevated, as expressed by the pressure-time index,[13] should be considered in sustained exercise and mild hypertension and help evaluate the benefits and harms of the two conditions. Whether in some cases mild hypertension may act as beneficial as exercise for the heart is worth further study.

References

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  2. References
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