Hemodynamic response: decrease in cardiac output vs reduction in vascular resistance

Impact of Cardiovascular Factors on Pulse Wave Velocity and T otal Vascular Resistance in Different Age Group Patients with Cardiovascular Disorders

Background: Pulse Wave Velocity (PWV) is the propagation speed of the wave-induced along the aorta and arterial tree, each time the heart beats. PWV increases with increased arterial stiffness, thus establishing it as a reliable prognostic marker for cardiovascular morbidity and mortality. On the other hand, Total Vascular Resistance (TVR) is the overall resistance offered by systemic circulation and pulmonary circulation. This resistance needs to be overcome in order to create the flow of blood through the circulatory system. The goal of this study was to investigate the influence of different cardiovascular factors on arterial stiffness and vascular resistance in CVD patient from eastern India population.

Methods: Total of 782 patients with Cardiovascular Disease (CVD) like hypertension, Ischemic heart disease, Congestive cardiac failure and peripheral arterial disease were included to evaluate the cardiovascular hemodynamic and non-hemodynamic parameter by oscillometric method and investigated those factors on PWV and TVR in subjects of both sexes aged between 15 to 87 years.

Results: The old age (> 55 years) was found to have greatest impact on PWV as compared with younger age group. Systolic Blood Pressure (SBP), Heart Rate (HR), augmentation pressure and Body Surface Area (BSA) had a positive association with the PWV. Augmentation Index and Body Mass Index (BMI) had a negative impact on the PWV.

Conclusion: Despite the limitations, like unequal number of male and female participants, wide variation of the age of the subjects and analyzing association of many factors at a time, our large and community-based study show individual blood pressure and pulse pressure depending on complex interaction between large arteries and arterioles. This study sheds light on the relationship between proximal and distal part (PWV and TVR) of the arterial tree as well as their association with different hemodynamic and non-hemodynamic parameters.

Exercise hemodynamics and oxygen delivery in human hypertension. Response to verapamil

To characterize the hemodynamic response to exercise and the effects of calcium channel antagonism in hypertensive subjects, invasive exercise hemodynamics were performed in the baseline state after intravenous infusion of verapamil and after 5 to 7 days of oral verapamil in 10 subjects with moderate to severe hypertension. We also assessed oxygen delivery and use and the response of the sympathetic nervous system by measuring plasma norepinephrine levels at rest and during exercise. Both routes of administration were associated with significant reductions of mean arterial pressure and systemic vascular resistance at rest and peak exercise (p less than 0.05). Changes in heart rate were not statistically significant. Following oral administration of verapamil, stroke volume increased significantly in both the resting and exercise states. Pulmonary wedge pressure did not increase; in fact, the Frank-Starling relationship of cardiac performance actually was improved. Oxygen delivery and use were unchanged with both routes of administration. There was no significant difference in rest and exercise plasma norepinephrine levels following verapamil therapy. Thus, verapamil resulted in a significant reduction of mean arterial pressure, mediated by a significant reduction of systemic vascular resistance, following both intravenous and short-term oral administration. This reduction occurred without expression of left ventricular dysfunction and was not at the expense of increased oxygen use or enhanced sympathetic nervous systemic activity.

Oral nifedipine for the treatment of patients with severe hypertension

Ten mg of nifedipine was administered to 19 patients with severe hypertension (mean blood pressure 187 +/- 17/122 +/- 12 mm Hg) without intensive care monitoring. Patients were instructed to bite and swallow the contents of the capsule. Blood pressure declined significantly to a mean of 149 +/- 17/92 +/- 10 mm Hg. No adverse side effects or hypotension occurred. Ten patients required an additional dose 30 to 60 minutes after the initial dose. Mean heart rate increased from 79 to 95 beats per minute without symptomatic consequences. Laboratory parameters measured before and after the four-hour study did not change significantly, although peripheral renin activity rose transiently. Urinary sodium excretion increased 43 percent over four hours after therapy in three patients in whom it was measured. Cardiac output, which was measured noninvasively in seven patients, rose nonsignificantly whereas systemic vascular resistance declined from 2,070 dynes/second/cm-5 to 1,271 dynes/second/cm-5 (statistically significant difference) in 20 minutes. These results indicate that oral nifedipine, when bitten and swallowed, effectively lowers blood pressure in patients with severe hypertension without the occurrence of adverse side effects or hypotension. Oral nifedipine may be used safely in an outpatient setting when urgent intervention is required.