Total effective compliance of the vascular bed in essential hypertension

Total effective vascular compliance, hemodynamic parameters, cardiopulmonary (CPBV) and total blood volumes (TBV) were determined in 31 men, including nine normotensive controls and 22 permanent essential hypertensive patients. The effective compliance was calculated from the changes in central venous pressure recorded simultaneously with the changes in blood volume obtained after a rapid dextran infusion. In hypertensives, compliance was significantly reduced (1.55 +/- 0.6 vs 2.25 +/- 0.11 ml./mm. Hg/Kg. in controls) (P less than 0.001) and negatively correlated with blood pressure (P less than 0.01), cardiac index (P less than 0.01), and the CPBV/TBV ratio (P less than 0.01). These results suggest that venous compliance contributes to the control of cardiac output in essential hypertension.     

Hemodynamic study of 85 patients with borderline hypertension

Hemodynamic changes in supine and upright position (50 ° head-up tilt) and during exercise were studied in 40 normal subjects and 85 patients with borderline hypertension. The latter were classified in 2 groups, according to the level of cardiac index. In group I, with patients in the supine position, cardiac index, stroke index, heart rate and plasma volume were normal, but total peripheral resistance was increased (P < 0.01). During upright tilt, orthostatic decrease of mean arterial pressure (P < 0.05) was observed, and the increase in total peripheral resistance was not greater than in normal subjects. The hemodynamic response to exercise was similar to that of normal subjects. In patients in group II, cardiac index, stroke index and heart rate were increased (P < 0.001), but plasma volume was decreased (P < 0.01) and total peripheral resistance was below normal (P < 0.001). With patients in the upright position, diastolic orthostatic hypertension was observed (P < 0.001) and total peripheral resistance was greater than normal (P < 0.01) despite an abnormal fall of cardiac index (P < 0.05). The hemodynamic response to exercise indicated that total peripheral resistance did not decrease as in normal subjects and in patients of group I (P < 0.001). This study provides evidence that (1) total peripheral resistance is abnormal in patients with borderline hypertension, but only during upright tilt and exercise in patients with high cardiac index, and (2) 2 main disorders seem to be important in the early stage of hypertension: abnormality of blood volume (or blood volume distribution, or both) and impaired neurogenic activity.     

Prospective study of predictive factors determining borderline hypertensive individuals who develop sustained hypertension: Prognostic value of increased diastolic orthostatic blood pressure tilt-test response and subsequent weight gain

Repeat hemodynamic determinations in supine and tilting positions were performed in 23 young men with borderline hypertension (HBP). The mean duration of follow-up was 48 months. During the study 11 patients had no change in hemodynamic parameters (group II), while 12 patients exhibited significant increase in systolic (p < 0.001) and mean (p < 0.01) arterial pressures (BP) and in body weight (p < 0.05) (group I). In this latter group, the initial hemodynamic pattern included supine elevations in cardiac output (CO) and heart rate (HR) and significant increase in diastolic orthostatic BP. After follow-up, the group I primary supine increases in CO and HR were followed by secondary supine increases in total peripheral resistance (p < 0.01) and systolic (p < 0.001) and mean (p < 0.01) BP with lower CO (p < 0.05) and HR (p < 0.001). In addition, it was shown during long-term follow-up in group I patients that: (1) the increase in systolic BP per unit age was negatively correlated with initial age (p < 0.001), (2) the increase in BP was positively correlated with weight gain (p < 0.05), and (3) the diastolic orthostatic hypertension disappeared. This study provides evidence that, in patients with borderline HBP having supine elevations of CO and HR, the subsequent development of sustained HBP can be expected, with follow-up observation of lower supine HR and disappearance of diastolic orthostatic hypertension accompanied by rapid weight gain.     

Vascular reactivity to norepinephrine and hemodynamic parameters in borderline hypertension

Pressor response to norepinephrine, cardiopulmonary blood volume, and hemodynamic parameters were studied in 41 borderline hypertensive patients in comparison with 42 permanent essential hypertensive patients and 28 normal subjects. Borderline hypertensive subjects had a high cardiac index (p < 0.0001), normal total peripheral resistance, and low total blood volume (p < 0.005). The ratio between cardiopulmonary blood volume (CPBV) and total blood volume (TBV) was significantly higher in comparison with normal subjects (p < 0.01) and permanent hypertensive subjects (p < 0.001). The pressor dose of norepinephrine was elevated (p < 0.0001) and was directly correlated with the basal values of the cardiac output (p < 0.005), the cardiopulmonary blood volume (p < 0.001), and the $\text{CPBV}\text{TBV}$ ratio (p < 0.01). None of these results was observed in permanent hypertensive subjects: the only significant result was a negative correlation between the pressor dose of norepinephrine and the basal diastolic arterial pressure (p < 0.0001). This study provides evidence that the cardiac output elevation in borderline hypertensive subjects was related to increased venous return and enhanced sympathetic venous tone.     

Control of cardiac output in essential hypertension

Cardiac and renal hemodynamics and cardiopulmonary and total blood volume were determined in 202 men, 101 with normotension and 101 of the same age with chronic essential hypertension, normal renal function and balanced sodium intake and urinary output. Cardiac output was identical in the two groups, whereas blood pressure and total peripheral resistance were significantly different. The two groups exhibited strong differences in the correlation study: (1) Correlations of blood pressure with, respectively, heart rate, cardiopulmonary blood volume and total blood volume were significant in the normotensive group but not in the hypertensive group. (2) Correlations of cardiac output with, respectively, heart rate, cardiopulmonary blood volume and total blood volume were significant in both groups. (3) Correlations of renal blood flow with, respectively, cardiac output, blood pressure and total blood volume were significant in the hypertensive group but not in the normotensive group.This study provides evidence that: (1) the volume and neural control of blood pressure are disrupted in hypertension whereas control of cardiac output is maintained; and (2) adaptive mechanisms involving renal function are necessary to the maintenance of normal cardiac output in patients with essential hypertension.     

Repeat hemodynamic determinations in borderline hypertension

Repeat hemodynamic determinations were performed in 37 young men with borderline hypertension. The duration of the follow up study was 47 ± three months. At each determination, those with borderline hypertension were compared to a group of matched normal subjects. Blood pressure increased from the first to the second determination, but the increase was significant only for systolic (P < 0.001) and mean (P < 0.01) arterial pressures. Cardiac index and heart rate, which were initially increased, decreased significantly (P < 0.02; P < 3.01, respectively) and decreased to normal values; total peripheral resistance increased (P < 0.01); blood and plasma volumes decreased (P < 0.01). At the first determination, the cardiac index-heart rate correlation was significant (P < 0.01) and the cardiac index-blood volume correlation was not. At the second determination, on the contrary, the cardiac index-total blood volume correlation was significant (P < 0.001) whereas the cardiac index-heart rate correlation was not. The study provides evidence that patients with borderline hypertension, over a short-term period, show (1) a greater increase in systolic than in diastolic pressure, (2) a return of cardiac output toward normal values through a decrease both in heart rate and blood volume, and (3) an increased importance of volume factors in the cardiac output control.