Beta blockers and left ventricular hypertrophy in hypertension

It is now generally accepted that hypertension-induced left ventricular hypertrophy (LVH) represents a phenomenon of multifactorial origin. Antihypertensive therapy with beta-blocking drugs influences most of the factors involved in the control of left ventricular mass. Therefore, although initial animal experiments yielded conflicting results, it is not surprising that a great deal of evidence has been accumulated in clinical studies showing that successful long-term antihypertensive treatment with beta blockers induces regression of LVH in hypertensive subjects. Differences in molecular structure among various beta-blocking agents do not seem to influence this property. On the contrary, the question of whether reversal of LVH represents a beneficial or harmful byproduct of antihypertensive treatment with beta blockers is still unanswered. Animal and clinical studies suggest that left ventricular systolic function is unchanged or even improved after regression of LVH, whereas the ability of the heart to withstand recurrence of hypertension is slightly reduced. Furthermore, development of LVH in hypertensive subjects is associated with abnormalities in diastolic function which are not reduced by reversal of LVH induced by antihypertensive treatment with beta blockers.

Effects of celiprolol on systemic and forearm circulation in hypertensive patients: a double-blind cross-over study versus metoprolol

The antihypertensive efficacy of a new beta-receptor blocking agent, celiprolol, was compared with that of a well-established antihypertensive drug, metoprolol. Their systemic and forearm hemodynamic effects were investigated using echocardiography and two-dimensional pulsed Doppler flowmetry, respectively. Twenty hypertensive patients completed a double-blind, cross-over, randomized study using celiprolol and metoprolol. Two six-week courses with celiprolol or metoprolol were preceded and followed by a two-week placebo period; the total duration of the study was 18 weeks. In spite of a comparable efficacy in reducing systolic and diastolic blood pressure (about 10% of the basal value), the two drugs showed quite different systemic and regional hemodynamic effects. Celiprolol induced a significant decrease in forearm vascular resistance (from 157 +/- 17 to 113 +/- 13 mm Hg/mL/s, P less than .01) and total peripheral resistance (from 1596 +/- 90 to 1398 +/- 91 dyne.s.cm-5, P less than .05) whereas cardiac output remained unchanged and forearm blood flow increased. Metoprolol reduced cardiac output (from 6.5 +/- 3 to 5.7 +/- 3 L/min, P less than .05), through a reduction in heart rate, since stroke volume was unchanged. Both drugs did not significantly modify cardiac performance, as evaluated by left ventricle fractional shortening and ejection fraction. Thus, the two drugs seem to reduce blood pressure through different hemodynamic mechanisms.

Changes in left ventricular anatomy and systemic hemodynamics induced by antihypertensive therapy with indenolol

In 20 patients with mild or moderate essential hypertension who responded favorably to indenolol antihypertensive therapy, echocardiography was performed in the basal condition and 6 and 12 months after the beginning of permanent antihypertensive treatment. Indenolol induced a significant decrease in blood pressure, from a basal value of 170 +/- 3/100 +/- 8 mmHg to 142 +/- 4/87 +/- 2 mmHg after 6 months (p less than 0.01) and to 133 +/- 4/84 +/- 2 mmHg after 1 year (p less than 0.01), and in heart rate, from 72 +/- 5 to 61 +/- 3 bpm after 6 months (p less than 0.01) and to 60 +/- 2 bpm after 1 year (p less than 0.01). Simultaneously, there was a significant reduction in cardiac output (from 6.3 +/- .4 to 5.7 +/- .2 liters/min after 6 months, p less than 0.05, and to 5.6 +/- .2 liters/min after 1 year, p less than 0.01), due to a reduction in heart rate, increased stroke volume, and improved left ventricular performance after indenolol. Total peripheral resistance was also reduced, although statistical significance was not attained. However, a significant inverse correlation was found between the initial value of cardiac output and total peripheral resistance and the changes in these parameters induced by indenolol treatment (cardiac output: r = -0.824 and -0.855, total peripheral resistance: r = -0.876 and -0.899 at 6- and 12-month controls, respectively, all p less than 0.001). Finally, there was a parallel decrease in left ventricular wall and septal thickness and estimated left ventricular mass in patients with left ventricular hypertrophy, whereas no change in left ventricular anatomy could be detected in patients with normal left ventricular mass.

Effects of coronary occlusion on arterial baroreflex control of heart rate and vascular resistance

This study was planned to assess whether circumflex coronary occlusion (CO) impairs the arterial baroreflex control of heart rate (HR) and hindlimb vascular resistance (HVR), and to determine the mechanisms involved in the mediation of these phenomena. Increasing doses of phenylephrine and nitroglycerin were given intravenously to anesthetized dogs with a constant flow-perfused hindlimb before and during 30-s CO. The reflex responses were assessed by the changes in HR and hindlimb perfusion pressure evoked by changes in arterial pressure following phenylephrine and nitroglycerin administration. During CO, there was an attenuation of the reflex control of HR and HVR as compared with control conditions. The application of lidocaine on the left ventricular epicardial surface was able to prevent the effect of CO on both the baroreflex responses. The intravenous administration of atropine prevented only the impairment in arterial baroreflex control of HR induced by CO. After the injection of phentolamine into the perfused hindlimb, the baroreflex had no effect on HVR either before or during CO. Finally, intravenous administration of propranolol failed to modify the effect of CO on both the baroreflex responses. These data indicate that CO attenuates the arterial baroreflex control of both HR and HVR through the stimulation of left ventricular receptors. The effect on HR is mediated by the parasympathetic system, whereas the effect on HVR is due to sympathetic efferents.

Effects of intravenous verapamil administration on left ventricular diastolic function in systemic hypertension

The effects of intravenous verapamil administration (0.1 mg/kg as a bolus followed by an infusion of 0.007 mg/kg/min) were studied using high-temporal-resolution radionuclide angiography in 27 patients with hypertension. Verapamil administration increased heart rate from 69 +/- 11 to 75 +/- 12 beats/min (p less than 0.001) and decreased systolic, diastolic and mean blood pressures (BPs) from 155 +/- 21/102 +/- 12 mm Hg (mean 119 +/- 14) to 142 +/- 19/95 +/- 12 mm Hg (mean 109 +/- 13) (p less than 0.001 for all). Ejection fraction decreased significantly (from 65 +/- 10% to 60 +/- 11%, p less than 0.005); peak filling rate, however, increased significantly only in patients in whom it was subnormal in the basal study (from 2.2 +/- 0.4 to 3.0 +/- 0.6 end-diastolic counts/s, p less than 0.001). These latter patients had significantly higher values of left ventricular (LV) mass index than patients with normal or increased peak filling rate (129 +/- 22 vs 112 +/- 22 g/m2, respectively, p less than 0.05). The isovolumic relaxation period changes were inversely related to the baseline values (r = 0.83, p less than 0.001). In the subgroup of patients in whom isovolumic relaxation period lengthened, time to end systole decreased (from 360 +/- 31 to 329 +/- 30 ms, p less than 0.025) and time to onset of rapid filling increased (from 420 +/- 31 to 451 +/- 34 ms, p less than 0.025), whereas these 2 intervals had opposite patterns in patients in whom isovolumic relaxation period decreased or did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of lower body negative pressure in hypertensive patients with left ventricular hypertrophy

We studied the response of forearm vascular resistance to lower body negative pressure (LBNP) at -10 and -40 mmHg in seven established hypertensives with left ventricular hypertrophy (LVH) and seven age-matched normotensive controls. To evaluate the specific role of ventricular baroreceptors, we also investigated the effects of propranolol on the reflex response. Under control conditions, graded LBNP induced a progressive decrease in central venous pressure (CVP) and increased forearm vascular resistance. Changes in CVP and forearm vascular resistance were inversely correlated both in controls (r = -0.944) and in hypertensives (r = -0.960), P less than 0.001 for both. No difference was found between the regression slopes obtained for the two groups (normotensives, -30; hypertensives, -40; NS). After propranolol there was a significant reduction in the increase in forearm vascular resistance induced by -40 mmHg LBNP in normotensives but not in hypertensives. Consequently, the slope of the regression delta CVP/delta forearm vascular resistance was reduced in normotensives (-21) but not in hypertensives. In contrast, propranolol did not attenuate the vasoconstrictor response to other stimuli. Left ventricular hypertrophy therefore seems to be associated with changes in the role of the different cardiopulmonary receptor areas during mediation of the haemodynamic response to stimulated orthostatic stress.

Impaired responsiveness of the ventricular sensory receptor in hypertensive patients with left ventricular hypertrophy

We studied the control of forearm vascular resistance (FVR) by cardiopulmonary receptors in seven patients with hypertension and left ventricular hypertrophy (LVH) and in seven normotensive control subjects. Increasing levels of lower body negative pressure (LBNP) (-10 and -40 mm Hg) induced a progressive decrease in central venous pressure (CVP) and an increase in FVR. The changes in these two variables were correlated both in normal subjects and patients with hypertension (slope for normal subjects = -29.9, for patients with hypertension = -40.3, NS). After propranolol, there was a significant reduction in the increase in FVR induced by -40 mm Hg LBNP in normal subjects (+107 +/- 5 vs +129 +/- 15 mm Hg/ml/sec, p less than .05) but not in patients with hypertension. Consequently, the slope of the delta CVP/delta FVR regression was reduced in normal subjects (-20.6, p less than .01) but not in patients with hypertension. In another seven normal subjects and seven patients with hypertension and LVH we assessed the effects of -10 and -40 mm Hg LBNP on left ventricular filling pressure (LVFP). LBNP induced similar changes in CVP, LVFP, and total peripheral resistance both in normal subjects and in patients with hypertension. Propranolol failed to modify the effects of LBNP on CVP and LVFP in both groups and reduced the response of total peripheral resistance to -40 mm Hg LBNP only in normal subjects. Propranolol did not reduce the response of FVR to the cold pressor test and sustained handgrip or the arterial baroreflex response to the injection of phenylephrine and increased neck tissue pressure. Thus, hypertension-induced LVH seems to be associated with a selective impairment of the left ventricular sensory receptors.

Effects of prostaglandin synthesis inhibition on sympathetic-and parasympathetic-mediated coronary hemodynamic responses

In chloralose-anesthetized dogs with the left circumflex coronary artery perfused at constant flow, the effects of indomethacin or naproxen on coronary and systemic responses to sympathetic and parasympathetic stimulation were evaluated. Sympathetic stimulation was evoked either by 1-min carotid artery occlusion or by epinephrine (5 micrograms) or norepinephrine (5 micrograms) intracoronary administration. Reflex or direct parasympathetic stimulation was produced by ouabain (40 micrograms) or acetylcholine (2.5 micrograms) injection, respectively, in the perfused coronary artery. The administration of indomethacin or naproxen reduced the integrated areas of coronary vasodilatation induced by epinephrine and norepinephrine. The extent of this reduction was dose-dependent with both indomethacin (epinephrine: r = 0.774, n = 35, P less than .001; norepinephrine: r = 0.766, n = 35, P less than .001; norepinephrine: r = 0.799, n = 35, P less than .001) up to 1.5 and 7 mg/kg, respectively. Further increase in dosage of both prostaglandin synthesis inhibitors failed to induce further reduction of integrated areas of coronary vasodilatation. In contrast, the maximum fall in coronary perfusion pressure, induced by both catecholamines, remained unmodified after inhibition of prostaglandin synthesis, whereas a faster return of the perfusion pressure to base line was observed. The extent of cyclooxygenase activity inhibition induced by indomethacin or naproxen, assessed through the radioimmunoassay of thromboxane B2, showed a consistent dose-dependent increase until complete inhibition was attained with 1.5 mg/kg of indomethacin and 7 mg/kg of naproxen. No significant change in the coronary and systemic hemodynamic response induced by carotid occlusion and by ouabain or acetylcholine intracoronary administration was observed. Furthermore, complete cyclooxygenase inhibition, induced by either indomethacin or naproxen, was able to reduce the coronary vasodilatation induced by isoproterenol (5 micrograms) intracoronary injection but failed to modify the coronary vasoconstriction elicited by both epinephrine and norepinephrine in propranolol-treated dogs. These data indicate that the prostaglandin system is involved in the coronary vasodilatation induced by humoral sympathetic stimulation, whereas coronary hemodynamic responses to both neural sympathetic or parasympathetic stimulation are not influenced by the administration of prostaglandin synthesis inhibitors.

Noninvasive techniques in clinical pharmacology. Time intervals in assessment of vasodilators in coronary artery disease

We enrolled 15 male volunteers with angiographic evidence of coronary artery disease (CAD) to investigate the effects of sublingual administration, on different days, at random, of placebo and three drugs with different action such as isosorbide dinitrate, nifedipine and molsidomine. We recorded simultaneously electrocardiogram, phonocardiogram and carotid pulse at paper speed of 100 mm/s; blood pressure was measured by auscultatory method. We calculated the systolic time intervals (STI) being noninvasive indices of left ventricular function and the ratio of diastolic time to heart rate (%D), well related to coronary blood flow in patients with severe obstructive lesions. Placebo decreased heart rate (HR) without effects on STI or %D. Isosorbide dinitrate induced a prolonged pre-ejection period (PEP) (by decreasing preload), tachycardia and a significantly decreased %D, suggesting a fall in coronary blood flow time. Nifedipine decreased diastolic blood pressure and values of PEP (by decreasing afterload) without effects on %D. Finally, molsidomine prolonged PEP (by decreasing preload) without reflex induced tachycardia and changes of %D. In conclusion, mechanocardiography can be useful in noninvasive assessment of vasodilators in CAD patients.

Reversal of left ventricular hypertrophy following treatment with beta-blockers: experience with tertatolol

Hypertrophy in response to increasing blood pressure in primary hypertension leads to important functional consequences for the left ventricle. In fact, the progression of hypertensive heart disease, from an adaptive left ventricular hypertrophy with compensated ventricular function to severe hypertrophy with left ventricular failure, has been long thought to be related to the severity and duration of hypertension. Antihypertensive treatment seems to prevent or minimize the occurrence of left ventricular hypertrophy, but questions arise as to whether this therapy is also able to restore normal hemodynamic conditions, or at least to minimize the hemodynamic abnormalities. This review aims at summarizing current knowledge on the effects of the antihypertensive treatment with beta-blockers, including tertatolol, on hypertension-induced left ventricular hypertrophy. The pathogenetic mechanisms underlying the cardiovascular changes associated with hypertension are discussed. A decrease in left ventricular wall thickness as well as in left ventricular mass has been reported in most of the studies performed with different types of beta-adrenergic blocking agents. The extent of this reduction seems to be related not only to the fall in systemic blood pressure, but also to a decrease in sympathetic stimulation. With regard to the functional consequences of hypertension, the reversal of left ventricular hypertrophy following antihypertensive treatment with beta-blockers is usually associated with an improvement in left ventricular performance. This phenomenon can hardly be ascribed to the direct effects of beta-blocking agents. It is more likely to be related to the concomitant reduction in the afterload and to the improved left ventricular compliance, associated with a decrease in left ventricular wall thickness.

Regulation of left ventricular mass by endogenous catecholamines in hypertensive progeny

In 10 normotensives with both parents hypertensive, the relationship between changes in echocardiographic parameters of left ventricular anatomy and those in circulating catecholamine levels induced by three 3-week periods of different sodium and potassium intakes were examined. A high-sodium normal-potassium regimen reduced upright plasma norepinephrine (P less than 0.01), posterior wall thickness (PWT) and interventricular septal thickness (IVST) as well as the left ventricular mass index (LVMi). Changes in upright plasma noreprinephrine correlated with those in IVST (r = 0.822, P less than 0.01) and in LVMi (r = 0.833, P less than 0.01). A low-sodium normal-potassium diet increased supine (P less than 0.001) and upright (P less than 0.01) plasma norepinephrine as well as the IVST and LVMi. The changes in supine and upright norepinephrine levels correlated with changes in IVST (r = 0.836 and r = 0.796 respectively, both P less than 0.01) and in LVMi (r = 0.931 and r = 0.947 respectively, both P less than 0.001). No significant change in any of the above parameters was detected after a low-sodium high-potassium regimen. These findings indicate that in hypertensive progeny catecholamines may play a role in the physiological regulation of left ventricular mass (LVM).

Indenolol: a new antihypertensive agent: efficacy, toxicity, and hemodynamic effects in a crossover double-blind study with metoprolol

The antihypertensive efficacy of a new agent, indenolol, was compared with that of the well-established antihypertensive drug, metoprolol, and its hemodynamic effects were investigated using echocardiography. Eighteen hypertensives completed a double-blind, crossover, randomized study using indenolol and metoprolol. Two four-week courses with indenolol or metoprolol were preceded and followed by a two-week placebo period; the total duration of the study was 14 weeks. Indenolol proved to be significantly more effective than metoprolol in decreasing blood pressure values at rest (P less than .05). Furthermore, three patients that failed with metoprolol were successfully treated with indenolol. Both drugs induced a significant decrease in cardiac output that was mediated mainly through a reduction in heart rate, because stroke volume, left ventricle circumferential fiber shortening velocity, and ejection fraction were not significantly reduced by either drug. However, after indenolol, a significant direct relationship was found between the basal values of both cardiac output (r = .809) and total peripheral resistance (r = .800), and the reduction of these parameters. On the contrary, after metoprolol only, the correlation between the basal value of cardiac output and its reduction was significant (r = .790).

Participation of endogenous catecholamines in the regulation of left ventricular mass in progeny of hypertensive parents

To investigate whether adrenergic activity is a determinant of left ventricular hypertrophy in human hypertension, in each of 10 normotensive subjects with two hypertensive parents we have examined the relationship between changes in echocardiographic parameters of left ventricular anatomy and those in circulating catecholamine levels induced by three, 3 week periods of different sodium and potassium intakes. A high sodium-normal potassium regimen induced a significant reduction in upright plasma norepinephrine (from 599 +/- 89 to 379 +/- 45 pg/ml, p less than .01) and in posterior wall (PWT) and interventricular septal (IVST) thickness, as well as in the left ventricular mass index (LVMi). Changes in upright plasma norepinephrine concentrations correlated with those in IVST (r = .822, p less than .01) and in LVMi (r = .833, p less than .01). A low sodium-normal potassium diet resulted in increases in supine and upright plasma norepinephrine levels (from 356 +/- 44 to 488 +/- 89 pg/ml, p less than .001; and from 565 +/- 42 to 744 +/- 33 pg/ml, p less than .01) as well as increases in IVST and LVMi (from 97 +/- 7 to 107 +/- 7 g/m2, p less than .001). The changes in norepinephrine levels in supine and upright subjects correlated with changes in IVST (r = .836, p less than .01 and r = .796, p less than .01) and in LVMi (r = .931, p less than .001 and r = .947, p less than .001). No significant change in plasma catecholamine concentrations or in PWT, IVST, or LVMi was detected after a low sodium-high potassium regimen.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid sinus reflex control of coronary blood flow in human subjects

Systemic and coronary hemodynamics were assessed before and during a reduction in carotid transmural pressure. This reduction was induced by means of a pneumatic neck chamber in 15 normal subjects and 15 hypertensive patients with a normal coronary arteriogram. A reduced baroreflex responsiveness was demonstrated in hypertensive patients as compared with normal subjects by evaluating both the reflex bradycardia evoked by intravenous administration of phenylephrine and the reflex increase in blood pressure during carotid sinus hypotension. In normal subjects, the reduction in carotid transmural pressure induced a significant increase in mean blood pressure, total peripheral resistance, cardiac output, heart rate, coronary vascular resistance, coronary blood flow assessed by the continuous thermodilution method and myocardial oxygen consumption. In hypertensive patients, the same stimulus significantly increased mean blood pressure, cardiac output, heart rate and coronary blood flow while no significant change was detected in coronary vascular resistance and myocardial oxygen consumption. The increase in mean blood pressure, total peripheral resistance and cardiac output was significantly higher in normal subjects than in hypertensive patients. These results suggest that in normal subjects carotid sinus hypotension evokes reflex coronary vasoconstriction, whereas this response is blunted in hypertensive patients with reduced baroreflex sensitivity.

Late phase of nitroglycerin-induced coronary vasodilatation blunted by inhibition of prostaglandin synthesis

In chloralose-anesthetized dogs with the left circumflex coronary artery perfused at constant flow, the effects of increasing doses of indomethacin or naproxen on the coronary and systemic hemodynamic responses to a 5 microgram intracoronary injection of nitroglycerin (NTG) were evaluated. The integrated areas of NTG-induced coronary vasodilatation were reduced after administration of indomethacin or naproxen. The extent of this reduction was increased progressively by augmenting the dose of indomethacin and naproxen up to 1.5 and 7 mg/kg, respectively. We also assessed the extent of cyclooxygenase inhibition induced by indomethacin or naproxen through the radioimmunoassay of thromboxane B2, which reflects thrombin-induced activation of platelet thromboxane A2 production during whole blood clotting. The level of inhibition progressively increased and complete inhibition was attained with 1.5 mg/kg indomethacin and 7 mg/kg naproxen. Further increase in dosage failed to induce further reduction of integrated areas of coronary vasodilatation, and a correlation was found between the extent of the reduction of the integrated areas of coronary vasodilatation and the dose of indomethacin (r = .828, n = 35, p less than .001) or naproxen (r = .729, n = 35, p less than .001). Finally, the NTG-induced maximum fall in coronary perfusion pressure remained unmodified after inhibition of prostaglandin synthesis, but there was a faster return of the perfusion pressure to the basal value.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of prostaglandins in the renal handling of a salt load in essential hypertension

Renal function and systemic hemodynamics were assessed in 10 hypertensive patients and in 10 age-matched normotensive subjects during control conditions (80 mEq of sodium/day) and after a salt load, either alone (480 mEq/day) or combined with indomethacin or sulindac. Indomethacin was used to induce ubiquitous inhibition of prostaglandin synthesis and sulindac to inhibit prostaglandin synthesis in all tissues except the kidney. Under control conditions there was no significant difference between the 2 groups in any measurement except blood pressure and total peripheral resistance. Also, the changes induced by salt load in the 2 groups were comparable. However, after indomethacin administration, only hypertensive patients showed a significant reduction in the 24-hour sodium excretion (from 417 +/- 61 to 317 +/- 49 mEq, p less than 0.05), so that the difference between this value and the corresponding value of normotensive subjects (453 +/- 79 mEq) became significant (p less than 0.05). The changes in sodium excretion in hypertensive patients were significantly correlated with the changes in renal plasma flow (r = 0.803, p less than 0.01). However, cardiac output and renal blood flow showed a similar pattern in normal and hypertensive persons. Finally, after the addition of sulindac to salt load, the differences in the 24-hour sodium excretion vanished. These results were also confirmed in an ancillary study performed, using the same protocol, in 10 other hypertensive patients using ibuprofen rather than indomethacin. Our data suggest that renal prostaglandins participate in renal disposal of chronic salt load in hypertensive patients but not in normal persons.

Efficacy of a new antihypertensive agent (indenolol) assessed by ambulatory blood pressure monitoring

The effects of two-week treatment periods with indenolol (I) and metoprolol (M) were examined by 24-hour mean blood pressure (BP) monitoring in control conditions and during exercise stress test in 7 patients with essential hypertension, using the Oxford method. Both drugs induced a significant reduction in mean BP and heart rate (HR) as compared to pretreatment values (mean BP: from 117 +/- 3 mmHg to 106 +/- 4 after I, p less than 0.05 and to 102 +/- 3 after M, p less than 0.01; HR: from 78 +/- 2 bpm to 66 +/- 2 after I, p less than 0.01 and to 67 +/- 2 after M, p less than 0.01). I and M induced a significant reduction in systolic and diastolic BP throughout the day and most of the night. During bicycle ergometer the basal and peak values of systolic and diastolic BP were significantly lower after both treatments as compared to the pretreatment values (both p less than 0.01). Our data suggest that I once a day possesses a substantial and consistent antihypertensive action, effective over most of the 24 hours.

Postural changes and isosorbide dinitrate. A polygraphic study in patients with coronary artery disease

Sitting or orthostatic positions and trinitrine-like drugs reduce venous return. We focused on the non-invasive assessment of postural-induced cardiovascular stress and isosorbide dinitrate (IDN) induced changes in 8 male patients with coronary artery disease (CAD), using polygraphic recordings by means of a Thermistor Pulse Transducer. The pre-ejection period (PEP) is sensitive to reduced preload and to the positive inotropic state of the myocardium. In addition, the % diastole (RR interval--electromechanical systole/RR interval) has been recently demonstrated to be correlated to coronary perfusion in CAD patients. We observed that IDN in clinostatism and the sitting position reduced preload (longer PEP) with increased heart rate (HR) and did not affect % diastole. In orthostatism, while controls showed an increased HR and prolonged PEP, the HR was higher after IDN, with a fall in PEP and a significant decrease in % diastole. We ascribed this change to adrenergic stimulation by the hypotensive actions of IDN (lowered mean blood pressure) in orthostatism and with a fall in coronary perfusion. Caution should be taken in CAD patients when postural stress could occur during IDN treatment. Moreover, polygraphic studies can be useful to detect individual responses to nitrates and serial recordings could be employed to assess late responses to chronic management with IDN.

Diltiazem in the treatment of mild or moderate essential hypertension. Comparison with metoprolol in a crossover double-blind trial

The antihypertensive efficacy and tolerability of a calcium antagonist drug, diltiazem (60 mg q.i.d. per os), was compared with that of metoprolol (100 mg b.i.d. pr os) in a crossover, double-blind randomized trial in 20 patients with mild or moderate essential hypertension. Blood pressure and heart rate were assessed at rest and during bicycle exercise before and after four-week periods of treatment. Both metoprolol and diltiazem reduced significantly systolic and diastolic blood pressure, while heart rate decreased only after metoprolol therapy. The reduction in blood pressure and the percentage of patients who responded favorably were similar with the two drugs. Furthermore, the overall levels of blood pressure during exercise were significantly reduced by both treatments, while only metoprolol was able to reduce the maximum increase in systolic blood pressure and heart rate induced by exercise. These results suggest that the use of diltiazem may be appropriate to the treatment of patients with mild or moderate essential hypertension.

Ouabain-induced reflex coronary vasodilatation mediated by cardiac receptors

Experiments were performed to determine the effects of digitalis-induced stimulation of cardiac receptors on the coronary circulation. In chloralose-anesthetized dogs, left circumflex coronary artery was perfused at constant flow, and heart rate was maintained constant by electric pacing. Ouabain injection in the perfused coronary artery produced a significant decrease in coronary perfusion pressure. Epicardial application of lidocaine completely blocked the reflex response. Vagotomy also prevented this reflex response. Sympathetic blockade with intravenous guanethidine or intracoronary phentolamine partially reduced the reflex coronary vasodilatation. Intracoronary atropine also partially reduced the coronary vasodilator response to ouabain. The combined administration of guanethidine and atropine completely abolished the coronary reflex response. These data demonstrate that ouabain can evoke reflex coronary vasodilation by stimulating cardiac receptors. This reflex response is mediated by activating cholinergic vasodilator fibers and inhibiting sympathetic vasoconstrictor fibers.

Effect of acebutolol on left ventricular hemodynamics and anatomy in systemic hypertension

In 18 patients with mild or moderate essential hypertension who responded favorably to acebutolol antihypertensive therapy, echocardiography (echo) was performed in the basal condition and after 6 and 12 months of follow-up. Acebutolol induced a significant decrease in blood pressure (BP), from a basal value of 167 +/- 3/105 +/- 2 mm Hg to 138 +/- 5/90 +/- 2 mm Hg after 6 months (p less than 0.01) and to 134 +/- 3/91 +/- 3 mm Hg after 1 year (p less than 0.01), and in heart rate, from 75 +/- 3 to 63 +/- 2 beats/min after 6 months (p less than 0.01) and to 63 +/- 2 beats/min after 1 year (p less than 0.01). The decrease in BP was achieved through a decrease in cardiac output from 6.3 +/- 0.28 to 5.3 +/- 0.25 liters/min after 6 months (p less than 0.05) and to 5.32 +/- 0.2 liters/min after 1 year (p less than 0.05), which resulted from a reduction in heart rate; stroke volume did not show significant change during the treatment and left ventricular (LV) performance was improved. There was a parallel decrease in LV posterior wall and ventricular septal thicknesses and estimated LV mass. In patients with LV hypertrophy, the change in mass was significantly correlated with the change in heart rate both after 6 and 12 months of therapy (r = 0.6234, p less than 0.05 and r = 0.7121, p less than 0.05 after 6 and 12 months, respectively).

QT/QS2 ratio as an index of autonomic tone changes

The effects of changes in sympathetic tone on QT/QS2 ratio were studied in 10 healthy subjects aged 21 to 24 years. The subjects underwent a bicycle ergometer exercise, a tilt test, a decrease in carotid transmural pressure induced by means of pneumatic neck chamber, an i.v. injection of phenylephrine. A phonocardiogram and ECG were simultaneously recorded at a paper speed of 100 mm/s to evaluate QT and QS2 intervals in each test. In basal conditions, the QT/QS2 ratio was less than 1, whereas it increased progressively during the physical exercise and became greater than 1 at peak exercise. Both the upright position and the increase in neck-tissue pressure induced a significant increase in the QT/QS2 ratio as compared with the basal values, whereas i.v. administration of phenylephrine reduced significantly the QT/QS2 ratio. These results demonstrate that those stimuli which induce a rise in adrenergic activity may increase the QT/QS2 ratio. In contrast, the reflex inhibition of the adrenergic activity induced by phenylephrine is accompanied by a reduction in QT/QS2 ratio. Therefore, the QT/QS2 ratio might represent a reliable index of sympathetic cardiac tone.

Relationships between left ventricular mass and clinical, biohumoral and hemodynamic parameters in human hypertension

The relationships between left ventricular mass (LVM), assessed by echocardiography, and several biohumoral and hemodynamic parameters were studied in 63 mild or moderate hypertensive patients and in an age-matched group of 23 normotensive subjects. In hypertensive patients, but not in normotensives, LVM index was significantly correlated with beta-adrenoceptor responsiveness, as evaluated by the chronotropic response to isoproterenol ( CD25 ) (r = 0.525, p less than 0.001) and with the 24-hour catecholamine urinary output (r = 0.485, p less than 0.001). Both CD25 and the catecholamine urinary output were significantly higher in the hypertensives as compared with the normotensive subjects. Moreover, left ventricular wall thickness (septum + posterior wall) was significantly correlated with CD25 and urinary catecholamines only in hypertensive patients. No significant correlation was found between LVM or wall thickness and body surface area, age, blood pressure, heart rate, cardiac output, total peripheral resistance and left ventricular systolic wall stress, whereas CD25 was correlated with urinary catecholamines only in hypertensive patients (r = 0.606, p less than 0.001). These results seem to support the hypothesis that an elevated adrenergic tone may exert a permissive role in the development of left ventricular hypertrophy in human hypertension.

Predictability of antihypertensive efficacy of selective beta 1 blockers

The possibility that hemodynamic and biohumoral factors may help predict the antihypertensive effectiveness of selective beta 1 blockers was investigated. The effects of 3 wk of treatment with two selective beta 1 blockers, metoprolol and atenolol, were observed in 54 patients with mild or moderate essential hypertension. No significant difference between the hemodynamic effects of the two drugs was found. The percent fall in systolic blood pressure induced by the two correlated strongly with the pretreatment values of the chronotropic response to isoproterenol and with the pretreatment values of cardiac output, heart rate, and plasma renin activity (PRA). There was no correlation between the decrease in systolic blood pressure induced and initial 24-hr urinary catecholamine output, total peripheral resistance, and plasma aldosterone. Percent fall in diastolic blood pressure correlated only with the pretreatment levels of PRA. Our results support the view that the hypotensive effect of beta 1 blockers are predictable on the basis of the pretreatment values of chronotropic response to isoproterenol, PRA, heart rate, and cardiac output.