Myocardial contrast echocardiography for the assessment of coronary blood flow reserve: validation in humans

OBJECTIVES

The aim of this study was to validate the use of myocardial contrast echocardiography to determine coronary blood flow reserve in humans.

BACKGROUND

Although myocardial contrast echocardiography has been used to accurately quantify coronary flow reserve in animals, validation for its use in humans to measure flow reserve is lacking.

METHODS

We analyzed the time-intensity curve from the anteroseptal region of the left ventricular short axis produced after a left main coronary artery injection of sonicated albumin before and after intracoronary administration of papaverine in 16 patients without angiographically significant coronary artery disease. The ratio of half-time of video intensity disappearance from peak intensity, variable of curve width, area under the time-intensity curve and corrected peak contrast intensity after papaverine compared with baseline were correlated with coronary flow reserve measured simultaneously with an intracoronary Doppler probe in the left anterior descending coronary artery.

RESULTS

There was a strong inverse correlation with half-time of contrast washout and coronary flow reserve (r = -0.76, p = 0.0007) and a strong positive correlation between the variable of curve width (which is inversely proportional to curve width) and coronary flow reserve (r = 0.71, p = 0.002). There was a weak but significant inverse correlation between area under the time-intensity curve and coronary flow reserve (r = -0.54, p = 0.03) but no correlation between corrected peak contrast intensity and coronary flow reserve (r = -0.36, p = NS). Despite the strong correlation for the ratios for half-time of contrast washout and variable of curve width and actual coronary flow reserve measured with intracoronary Doppler probe, the transit time ratios consistently underestimated coronary flow reserve.

CONCLUSIONS

Myocardial contrast echocardiography performed with left main coronary artery injections of sonicated albumin can be utilized to measure coronary flow reserve in humans. Transit time variable ratios (half-time of contrast washout and variable of curve width) derived from the time-intensity curve correlate most strongly with coronary flow reserve.

Natural history of disseminated Mycobacterium avium complex infection in AIDS

This study sought to better characterize the natural history of AIDS-associated disseminated Mycobacterium avium complex (MAC) infection. Towards that end two retrospective studies were done: a case-control survival study and a MAC respiratory colonization study. Among 137 consecutive patients who had a sterile body site cultured for mycobacteria within 3 months of their first AIDS-defining episode of Pneumocystis carinii pneumonia, median survival was significantly shorter in those with disseminated MAC infection (107 days; 95% confidence interval [CI] 55-179) than those with negative cultures (275 days; 95% CI 230-318; P less than .01), even after controlling for age, absolute lymphocyte count, and hemoglobin concentration. Among 34 patients with AIDS and respiratory MAC colonization, 22 later developed disseminated infection (65% predictive value for subsequent MAC dissemination). Disseminated MAC infection was associated with significantly shorter survival for patients with AIDS, and the presence of MAC in respiratory specimens has substantial predictive value for subsequent disseminated infection.

Lidocaine attenuates efferent sympathetic responses to stress in humans

The effects of antiarrhythmic doses of lidocaine on efferent sympathetic outflow or sympathetic responses to autonomic stimuli in humans are unknown. In the present study, direct recordings of postganglionic muscle sympathetic nerve activity (MSNA), which modulates vascular tone, were obtained from the peroneal nerve of 22 healthy volunteers (aged 20 to 27 years). Baseline cardiac intervals (ECG), arterial pressure (radial artery), central venous pressure (CVP, jugular vein), forearm vascular resistance (FVR, Hg-in-Silastic plethysmography), and MSNA were identical in two randomized study groups (lidocaine [L], 1.5 mg/kg bolus, followed by 2 mg/min infusion, n = 12; and placebo [P] saline bolus and infusion, n = 10). Each underwent a cold pressor test (CPT, ice packs to foot for 90 seconds) and baroreceptor test (sequential boluses of 100 micrograms of sodium nitroprusside and 100 micrograms of phenylephrine). Five minutes after the bolus administration of L, plasma L levels were 3 micrograms/mL, which was associated with significant (P less than 0.05) increases in systolic and diastolic pressures (6.6 +/- 2.4 and 5.5 +/- 1.1 mm Hg). This elicited significant reflex decreases in MSNA (-3 +/- 1.1 bursts/100 cardiac cycles) and RR interval (-63 +/- 14 ms). The hypertension, tachycardia, forearm vasoconstriction, and MSNA increase in response to the CPT were significantly attenuated and the sympathoexcitatory response to baroreceptor unloading was blunted by L. These responses were not altered during the administration of P. In the steady-state L infusion period, plasma levels were subtherapeutic (1 microgram/mL) and were insufficient to consistently alter autonomic stress responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Morbidity and mortality of patients with AIDS and first-episode Pneumocystis carinii pneumonia unaffected by concomitant pulmonary cytomegalovirus infection

To determine the significance of cytomegalovirus (CMV) pulmonary coinfection with Pneumocystis carinii pneumonia in AIDS, we examined the association of long- and short-term survival and morbidity (as defined by length of hospital stay) with recovery of CMV from bronchoscopy specimens and an indirect measure of virus titer in bronchoalveolar lavage fluid (the time to develop CMV cytopathology in culture) in 111 patients diagnosed with a first episode of P. carinii pneumonia. Compared with 57 individuals from whom CMV was not isolated, the 54 individuals from whom CMV were isolated did not differ in baseline characteristics, long-term survival (213 versus 275 days, p = 0.97), acute death rate (19% in both, p = 1.0), or length of hospital stay (19.7 versus 21.1 days, p = 0.68). Also, the time to develop CMV cytopathology in culture did not correlate with acute or long-term survival. Our observations thus do not support the use of CMV-specific antiviral therapy in AIDS patients with P. carinii pneumonia who also have evidence of pulmonary CMV infection.

Left ventricular diastolic collapse. An echocardiographic sign of regional cardiac tamponade

BACKGROUND

Cardiac tamponade after cardiac surgical procedures is often associated with hemodynamically significant localized pericardial effusions. The localized collection of pericardial effusion in the postoperative period and the atypical presentation of cardiac tamponade limit the use of conventional clinical and echocardiographic signs usually seen with a circumferential pericardial effusion. Observation of left ventricular diastolic collapse in the echocardiogram of a patient with postoperative regional cardiac tamponade prompted us to explore the frequency of this sign in regional cardiac tamponade.

METHODS AND RESULTS

We retrospectively analyzed the echocardiograms of 18 patients with postoperative cardiac tamponade for the following echocardiographic findings: right atrial collapse, right ventricular diastolic collapse, left atrial collapse, and left ventricular diastolic collapse. Three of the 18 patients had circumferential pericardial effusion, and 15 had loculated pericardial effusion; in 10, the effusion was predominantly posterior, and in the other five, it extended laterally or inferiorly. The conventional echocardiographic signs of cardiac tamponade such as right atrial collapse, right ventricular diastolic collapse, and left atrial collapse were present in only 3, 1, and 3 of these 15 patients, respectively, but all exhibited left ventricular diastolic collapse. Increasing pressure within the compartment of a loculated pericardial effusion reaching the limit of pericardial distensibility and consequent transient reversal of transmural left ventricular pressure during diastole are most likely the basis for diastolic collapse of the thick-walled ventricle in a setting of regional cardiac tamponade.

CONCLUSIONS

We conclude that left ventricular diastolic collapse is a frequent sign of regional cardiac tamponade and could be a useful marker of tamponade in postoperative patients.

Cyclosporine-induced sympathetic activation and hypertension after heart transplantation

BACKGROUND

Hypertension is a frequent complication of cyclosporine-induced immunosuppression, but the underlying mechanism is unknown. In anesthetized animals, the administration of cyclosporine increases sympathetic-nerve discharge, which may contribute to hypertension.

METHODS

To determine whether cyclosporine-induced hypertension is accompanied by sustained sympathetic neural activation in patients, we recorded sympathetic action potentials using intraneural microelectrodes (in the peroneal nerve) in heart-transplant recipients receiving azathioprine and prednisone alone (n = 5) or in combination with cyclosporine (n = 14). We performed the same studies in eight patients with myasthenia gravis who were receiving cyclosporine and eight who were not, in five patients with essential hypertension, and in nine normal controls.

RESULTS

Heart-transplant recipients receiving cyclosporine had higher mean arterial blood pressure (+/- SE) than those not receiving cyclosporine (112 +/- 3 vs. 96 +/- 4 mm Hg; P less than 0.05) and a 2.7-fold higher rate of sympathetic-nerve firing (80 +/- 3 vs. 30 +/- 4 bursts per minute; P less than 0.05). For patients with myasthenia gravis, similar doses of cyclosporine were associated with smaller elevations in mean arterial blood pressure (100 +/- 2 mm Hg, as compared with 91 +/- 4 mm Hg in those not receiving cyclosporine; P less than 0.05) and in the rate of sympathetic-nerve firing (46 +/- 3 bursts per minute, as compared with 25 +/- 4 bursts per minute; P less than 0.05). Sympathetic activity in patients with heart transplants or myasthenia gravis who were not being treated with cyclosporine was no different from that in patients with essential hypertension or in normal controls.

CONCLUSIONS

Cyclosporine-induced hypertension is associated with sympathetic neural activation, which may be accentuated by the cardiac denervation that results from heart transplantation.

Changes in regional adrenergic tone during sustained ventricular tachycardia associated with coronary artery disease or idiopathic dilated cardiomyopathy

The hemodynamic tolerance of an episode of ventricular tachycardia (VT) can vary widely from no decrease in systolic blood pressure to severe hypotension. Little is known about the factors responsible for these different responses in man. Previous animal studies have suggested an important role for vasoconstriction mediated by the alpha-adrenergic nervous system. To determine the magnitude and time course of changes in alpha-adrenergic tone during symptomatic sustained monomorphic VT, VT cycle length, mean and phasic arterial pressure, forearm blood flow (by venous occlusion plethysmography) and forearm vascular resistance were measured in 15 patients. Nine of these patients were studied before and after regional intraarterial alpha blockade with phentolamine. After the induction of VT (350 +/- 68 ms), mean forearm blood flow decreased from 3.2 +/- 1.1 to 2.2 +/- 0.8 ml/min/100 ml (p = 0.0002) and the forearm vascular resistance increased from 32 +/- 14 to 40 +/- 14 units (p = 0.01). There were no significant differences for forearm vascular resistance during the first and last 30 seconds of VT (41.3 +/- 14 vs 37 +/- 13 units). After the infusion of intraarterial phentolamine, there were no significant changes in the VT cycle length or mean arterial pressure, but the forearm vascular resistance increase during VT was blunted by 60 to 70%. Most patients with symptomatic VT demonstrate sympathetic vasoconstriction and these changes are maximal during the first 30 seconds of VT. This sympathoexcitatory response is due largely to stimulation of alpha-adrenoreceptors and may be mediated by arterial baroreflexes.

Autonomic pathophysiology in heart failure patients. Sympathetic-cholinergic interrelations

We conducted this study in an effort to characterize and understand vagal abnormalities in heart failure patients whose sympathetic activity is known. We measured sympathetic (peroneal nerve muscle sympathetic recordings and antecubital vein plasma norepinephrine levels) and vagal (R-R intervals and their standard deviations) activities in eight heart failure patients and eight age-matched healthy volunteers, before and after parasympathomimetic and parasympatholytic intravenous doses of atropine sulfate. At rest, sympathetic and parasympathetic outflows were related reciprocally: heart failure patients had high sympathetic and low parasympathetic outflows, and healthy subjects had low sympathetic and high parasympathetic outflows. Low dose atropine, which is known to increase the activity of central vagal-cardiac motoneurons, significantly increased R-R intervals in healthy subjects, but did not alter R-R intervals in heart failure patients. Thus, our data document reciprocal supranormal sympathetic and subnormal parasympathetic outflows in heart failure patients and suggest that these abnormalities result in part from abnormalities within the central nervous system.

New insights into pacemaker syndrome gained from hemodynamic, humoral and vascular responses during ventriculo-atrial pacing

Ventricular pacing is performed during programmed electrical stimulation and during normal functioning of single chamber (VVI or VVIR) pacemakers. In many patients, retrograde ventriculoatrial (V-A) conduction may occur and evoke hemodynamic and reflex neurohumoral responses, which are unique to this pacing mode. Accordingly, forearm blood flow, forearm vascular resistance, mean and phasic arterial pressure, cardiac output and plasma norepinephrine, epinephrine and dopamine were measured during atrial, ventricular and V-A pacing at a cycle length of 600 ms (100 beats/min) before and after regional alpha blockade with intraarterial phentolamine in 16 patients with a left ventricular ejection fraction greater than 35% and little or no symptoms of congestive heart failure. During V-A pacing, cardiac output decreased by 10%, whereas forearm vascular resistance increased from 52 +/- 7 to 70 +/- 9 U (p less than 0.001) and plasma norepinephrine increased from 183 +/- 27 to 232 +/- 27 pg/ml (p less than 0.01). Phentolamine nearly abolished the increase in forearm vascular resistance in response to V-A pacing (18 +/- 4.1 U before vs 5.8 +/- 1.5 U after, p less than 0.05). The change in forearm vascular resistance with V-A pacing correlated with systolic arterial pressure, but not with changes in mean arterial pressure, pulse pressure, cardiac output, mean or peak right atrial pressure, pulmonary artery or pulmonary capillary wedge pressure. These results suggest that forearm vascular resistance responses to V-A pacing are mediated mainly by alpha-adrenergic receptors, through the arterial baroreflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular sensory endings mediate reflex bradycardia during coronary arteriography in humans

It has been suggested that the response to the intracoronary injection of radiographic contrast is reflex in origin and results from stimulation of ventricular sensory endings. Cardiac transplantation results in denervation of the ventricles, and thus, may interrupt the afferent limb of this reflex. In contrast, the recipient sinus node and atrial remnant remain innervated, leaving the efferent cardiac limb of this reflex intact. We hypothesized that if contrast-induced reflex bradycardia and hypotension occurred from stimulation of ventricular chemosensitive endings, then this response would be abolished after cardiac transplantation. To test this hypothesis, we determined the changes in recipient (innervated) and donor (denervated) sinus-node rates (SNR) and mean arterial pressure during selective right (RCA) and left coronary artery (LCA) injection during arteriography in cardiac transplant patients and in patients with intact cardiac innervation. An increase in the recipient SNR was observed in cardiac transplant patients during left and right coronary injections (LCA, 6.6 +/- 1.7 beats/min; RCA, 2.4 +/- 1.4 beats/min) compared with a decrease in the control subjects (LCA, -15.3 +/- 2.3 beats/min; RCA, -6.9 +/- 1.9 beats/min; p less than 0.05 vs. control). This occurred despite significant and comparable decreases in mean arterial pressure in cardiac transplant patients (LCA, -12.7 +/- 2.3 mm Hg; RCA, -11.4 +/- 2.2 mm Hg) and control subjects (LCA, -18.7 +/- 1.7 mm Hg; RCA, -10.7 +/- 1.6 mm Hg). The donor SNR slowed for LCA injection (-5.4 +/- 2.1 beats/min, p less than 0.05) and RCA injection (-3.0 +/- 1.7 beats/min), which, for the LCA, was less than the slowing of control subjects (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Norepinephrine and forearm vascular resistance responses to tilt and cold pressor test in essential hypertension: effects of aging

Heart rate, blood pressure, forearm vascular resistance (FVR), and catecholamine and renin responses to head-up tilt at 80 degrees and cold pressor test were investigated in 15 hypertensive men aged less than fifty-five (mean 44 +/- 7 years; M +/- SD) and 13 similarly hypertensive men aged more than fifty-five (mean 62 +/- 4 years; M +/- SD). Baseline plasma norepinephrine levels, as well as norepinephrine responses to tilt and cold pressor stress, were similar in the two groups, suggesting a lack of age-related increase in plasma norepinephrine (NE) responses in patients with essential hypertension. Normalized FVR responses (% change) to tilting (28 +/- 21 vs 95 +/- 36; M +/- SE) and cold pressor test (33 +/- 12 vs 64 +/- 21; M +/- SE) were significantly less (p less than 0.01) in older hypertensives. These results, but not the plasma NE responses to reflex sympathetic activation by tilt and cold pressor testing in older hypertensives, suggest an impaired forearm vasoconstriction.

Atrial natriuretic peptide attenuates the reflex sympathetic responses to lower body negative pressure

The authors studied the effect of intravenous infusion of atrial natriuretic peptide (ANP) on the plasma catecholamine and forearm vasoconstrictor responses to cardiopulmonary baroreflex deactivation in six normal, male volunteers in order to determine whether ANP influences reflex forearm vasoconstriction in humans. Unloading of low-pressure cardiopulmonary baroreceptors (CPBR) was accomplished by application of low levels (-10 and -20 mm Hg) of lower body negative pressure (LBNP). The authors measured the plasma norepinephrine (NE) and epinephrine, the mean arterial pressure (MAP), and the forearm vascular resistance (FVR) responses to reflex sympathetic activation by LBNP. ANP infusion (0.1 microgram.kg-1.min-1) decreased (p less than 0.01) basal MAP, as well as plasma renin activity and plasma aldosterone levels (p less than 0.05). ANP infusion also reduced (p less than 0.01) plasma NE responses to both levels of LBNP and tended to decrease both epinephrine and FVR during ANP infusion at -20 mm Hg LBNP (p = 0.8). These data suggest that exogenous ANP inhibits the reflex sympathetic responses that occur with CPBR unloading. The blunted plasma NE responses to CPBR unloading parallel the attenuation of FVR response to LBNP during ANP infusion, despite significant LBNP-induced hypotension.

Neurohumoral and hemodynamic effects of lower body negative pressure in patients with congestive heart failure

Baroreflex modulation of forearm vascular resistance (FVR) has been reported to be abnormal in patients with congestive heart failure (CHF). However, the neurohumoral mechanisms for this impairment are not defined. We assessed the responses of arterial pressure, FVR, plasma norepinephrine, and plasma renin activity to lower body negative pressure in 29 patients with compensated CHF (New York Heart Association class III and IV) and in 11 normal age-matched control subjects. Baseline mean arterial pressure (83 +/- 2 vs 84 +/- 2 mm Hg) and mean arterial pressure during LBNP (-10, -20, and -40 mm Hg) were not significantly different in the two groups. Basal FVR (43.7 +/- 4 vs 27 +/- 2 units), plasma norepinephrine (605 +/- 81 vs 155 +/- 8 pg/ml), and plasma renin activity (8.3 +/- 1.7 vs 1.2 +/- 0.2 ng/ml/hr) were significantly (p less than 0.01) higher in patients with CHF. The relative increases in FVR responses during LBNP of -10, -20, and -40 mm Hg (10 +/- 4% vs 70 +/- 12%, 17 +/- 6% vs 106 +/- 21%, and 24 +/- 9% vs 152 +/- 28%) were markedly attenuated in patients with CHF compared to control subjects. Plasma norepinephrine and plasma renin activity responses during LBNP were also attenuated in patients with heart failure. Our results suggest that baroreflex control of FVR and plasma norepinephrine and plasma renin activity is impaired in CHF because of the inability of the cardiopulmonary baroreceptors to alter sympathetic outflow.

Detection of swine pox and buffalo pox viruses in cell culture using a protein A-horseradish peroxidase conjugate

Buffalo pox virus antigen was detected in Vero cells and swine pox virus antigen in the cytoplasm and nucleus of PK-15 and IB-RS-2 cells as early as 6 hr post infection (p.i.) by indirect immunoperoxidase technique using a Protein A-horseradish peroxidase (HRP) conjugate. The viral antigens localized in the cytoplasm of infected cells were the most prominent after 24 hr p.i.

Immune response induced by Vero cell culture adapted buffalo pox virus in rabbits and buffaloes

The Vero cell culture adapted buffalo pox virus was found to be completely attenuated at 40th passage for rabbits as well as buffaloes since it did not produce any thermal reaction or skin lesions. It induced high level of humoral and cell mediated immune response in rabbits as well as buffaloes. The antibody titres obtained were 80-160 for SN antibody, 32 for complement fixing and 640-1280 for enzyme immunoassay antibodies. The percent migration inhibition (MI) of leukocytes was 65.3% in rabbits and 69.50% in buffaloes, MI of macrophages was 62.15% in rabbits and 63.02% in buffaloes with a high skin reactive factor value. In protection tests conducted in rabbits and buffaloes, all the vaccinated animals were immune as compared to controls which showed severe disease.

Arterial baroreflex abnormalities in heart failure. Reversal after orthotopic cardiac transplantation

Arterial baroreflex control of the heart and peripheral circulation is markedly impaired in humans and animals with congestive heart failure. After reversal of heart failure in animal models, arterial baroreflex control of heart rate remains impaired for up to 8 months. Cardiac transplantation restores normal ventricular function and completely reverses heart failure, but does it normalize arterial baroreflex control of heart rate in humans? We studied baroreflex sensitivity in 11 patients with severe heart failure, six normal control patients, and 23 patients at 2 weeks to 4 years after orthotopic cardiac transplantation. Baroreflex sensitivity was assessed with intravenous bolus injections of phenylephrine and is expressed as change in RR or PP interval (msec) per millimeters of mercury rise in systolic arterial pressure. Atrial rate of both donor (denervated) and recipient (innervated) atria were measured in the transplant group. Baroreflex sensitivity in patients with severe heart failure was 2.0 +/- 0.3 msec/mm Hg, but in patients after cardiac transplantation, it was 13.0 +/- 0.9 msec/mm Hg (p less than 0.001). The responses in the transplant group were similar to those observed in normal controls (10 +/- 1.2 msec/mm Hg, p = NS). Our data indicate that patients with severe congestive heart failure have marked abnormalities of baroreflex control, which are reversed as early as 2 weeks after cardiac transplantation. In view of this rapid reversal, we consider it unlikely that abnormal baroreflex sensitivity seen in heart failure is due to structural alterations in the baroreceptors. We speculate that neurohumoral rather than structural abnormalities account for depressed baroreflex sensitivity in heart failure.

Effects of atrial natriuretic factor on urinary concentration of catecholamines and renin secretion in dogs

This study evaluated the effects of synthetic atrial natriuretic factor (ANF) on renal hemodynamics, urinary excretion of electrolytes, norepinephrine (NE), and dopamine (DA); and renal production of renin in anesthetized dogs. Following a bolus (1 micrograms/kg body weight) and infusion (0.1 microgram/kg/min) for 30 min, there was significant increase in urine flow (220 +/- 41%), glomerular filtration rate (72 +/- 14%), and urinary sodium excretion (170 +/- 34%). There was a decrease in renin secretory rate and the concentration ratio of urine NE to DA following ANF was decreased (p less than 0.05). These data suggest that ANF decreases renal production of NE and renin.

Increased circulating atrial natriuretic factor (ANF) release during induced ventricular tachycardia

During sustained ventricular tachycardia (VT), there is usually a rise in mean atrial pressure. Atrial natriuretic factor (ANF) is a peptide released by the atria in response to increased atrial pressure or distension. ANF causes arterial vasodilation and natriuresis in man, and may contribute to the polyuria noted during tachycardia. We hypothesized that induction of sustained VT would cause elevation of right atrial pressure and lead to increased release of ANF. We measured mean arterial pressure, right atrial pressure, VT cycle length, atrial cycle length, plasma norepinephrine, and central ANF in 11 patients during 20 episodes of VT. The mean cycle length of induced tachycardia was 335 +/- 15 msec, with a mean atrial cycle length of 547 +/- 43 msec. Baseline plasma ANF was 70 +/- 11 femtomoles per milliliter and increased to 133 +/- 22 fmol/ml (p less than 0.001) after 4 minutes of VT. There was a decrease in mean arterial pressure from 87 +/- 3 to 66 +/- 3 mm Hg, and a rise in mean right atrial pressure from 4.0 +/- 0.8 to 11 +/- 1 mm Hg (p less than 0.001). The change in plasma ANF was quite variable among individual patients and was correlated with changes in mean right atrial pressure but poorly correlated with changes in mean arterial pressure, plasma norepinephrine, and atrial cycle length. Our data demonstrate that significant increased in ANF levels occur during sustained VT and are associated with increased right atrial pressure.

Autonomic nervous system function

An age-related increase in autonomic nervous system activity, as reflected by increased plasma norepinephrine levels, has been reported by a number of investigators. This increase in plasma norepinephrine levels cannot be solely explained by increased obesity and decreased norepinephrine clearance with ageing. It has also been suggested that enhanced autonomic nervous system (sympathetic) activity may play a role in the pathogenesis of essential hypertension. However, recent studies from several laboratories have demonstrated that plasma norepinephrine levels increase with age in normotensives but not in patients with essential hypertension. A recent study from our laboratory has demonstrated no difference in basal or cardiopulmonary baroreflex-mediated increases in plasma norepinephrine levels in older hypertensives compared with middle-aged hypertensives. These observations suggest that elevated norepinephrine levels, per se, are not sufficient to explain the high prevalence of hypertension in the elderly, who are otherwise normal. In fact, it is likely that high norepinephrine levels in the elderly may be due to factors other than a primary hyperadrenergic state. Although arterial baroreceptor sensitivity decreases with ageing, studies from our laboratory indicate that cardiopulmonary baroreflex control of vascular resistance is relatively well preserved in older subjects with mild-to-moderate established essential hypertension. Thus, the relative influence of altered baroreflex sensitivity with ageing, or of a disturbed sympathetic outflow affecting autonomic nervous system activity and leading to variable blood pressure in the elderly, remains to be determined.

Atrial natriuretic factor release is enhanced by incremental atrial pacing

There is ample evidence from animal models indicating that secretion of atrial natriuretic factor (ANF) can be induced by an increase in atrial contraction frequency or atrial distension. The influence of these stimulatory signals on ANF secretion in humans has not been fully elucidated. We assessed the responses to graded right atrial pacing in 28 patients (aged 33 to 70 years) at rates of 100, 125, and 150 beats/min on right atrial pressure, left atrial size (by two-dimensional echocardiography in 9 of 28 patients), and circulating plasma ANF levels. At pacing rates of 125 and 150 beats/min, ANF levels increased from a baseline value of 64 +/- 9 fmol/ml (mean +/- SEM) to 89 +/- 13 fmol/ml (pp less than 0.05) and to 132 +/- 17 fmol/ml, respectively (p less than 0.001). Right atrial pressure increased from a baseline value of 4.1 +/- 0.7 mm Hg to 4.5 +/- 0.6 mm Hg at a pacing rate of 125 beats/min (p less than 0.05) and to 6.1 +/- 0.8 mm Hg at a pacing rate of 150 beats/min (p less than 0.001). Left atrial dimension increased from a baseline value of 44.5 +/- 3 mm to 49.5 +/- 3 mm at a pacing rate of 125 beats/min (p less than 0.05) and increased further to 52.5 +/- 3 mm at a pacing rate of 150 beats/min (p less than 0.001). No significant changes in atrial pressure or size or in plasma ANF were observed at a pacing rate of 100 beats/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Isradipine (PN 200-110) versus hydrochlorothiazide in mild to moderate hypertension. A multicenter study

The effects of 10 weeks of treatment with isradipine (ISRP), a new dihydropyridine Ca antagonist, was evaluated in a prospective, randomized, double-blind, parallel group, hydrochlorothiazide (HCTZ) controlled study in patients with mild to moderate hypertension. Of 98 patients enrolled, 73 completed the study and were deemed valid for efficacy analyses; 36 in the ISRP group and 37 in the HCTZ group. Monotherapy with ISRP significantly (P less than 0.001) decreased (mean +/- SD) sitting systolic blood pressure (BP) from 146 +/- 11 mm Hg to 128 +/- 11 mm Hg and diastolic BP from 100 +/- 4 mm Hg to 83 +/- 5 mm Hg. Heart rate during the plateau period was not significantly different (76 +/- 11 vs 78 +/- 11 bpm) between the ISRP and HCTZ groups. These reductions in BP were comparable to monotherapy with HCTZ. The mean reduction in diastolic BP with ISRP (17 +/- 6 mm Hg) was significantly (P less than 0.05) greater than that with HCTZ (14 +/- 5 mm Hg). The mean doses for ISRP and HCTZ were 12 mg/day and 60 mg/day, respectively. There was no significant difference in frequency of common side effects (headache, nausea, fatigue, dizziness, palpitations) between the two groups. However, transient or intermittent peripheral edema occurred more frequently in ISRP group. Four patients in ISRP group (two due to edema and two due to palpitations) and two patients in HCTZ group (due to poor BP control) were discontinued from the study. Our results indicate that ISRP in doses of 5 to 10 mg bid is as effective as HCTZ as monotherapy in the treatment of mild to moderate hypertension.

Clinical significance of pericardial effusion after heart transplantation

Fifty-two consecutive patients who underwent orthotopic heart transplantation at our institution were evaluated by two-dimensional (2D) echocardiography at frequent intervals for 12 weeks after transplantation and at three monthly intervals for 1 year. Thirty-eight of 52 patients had adequate 2D echocardiograms and comprised the retrospective study group. Pericardial effusion was documented in 15 of 38 patients (40%). Pericardial effusion was moderate in two (5%) and small in seven patients (18%). Large pericardial effusion was demonstrated in six of 38 patients (16%). Three of 38 patients (8%) developed cardiac tamponade manifested by hypotension in the presence of a large pericardial effusion. The diagnosis of cardiac tamponade was aided by 2D echocardiography leading to prompt pericardiocentesis. The presence of pericardial effusion in patients after their transplantation did not demonstrate independent correlation with chest tube output after operation, cyclosporine therapy, acute rejection, level of blood urea nitrogen (BUN), infection or preoperative diagnosis of idiopathic dilated cardiomyopathy. The presence of cyclosporine therapy, acute rejection, and a preoperative diagnosis of idiopathic dilated cardiomyopathy, however, yielded an 86% probability of having pericardial effusion. Follow-up 2D echocardiograms obtained 301 +/- 106 days after transplantation were available in 25 patients. Fifteen patients (60%) had no pericardial effusion present on either the initial or follow-up 2D echocardiogram. The majority of cases of the pericardial effusion present on initial or follow-up echocardiograms were resolving on the follow-up study.(ABSTRACT TRUNCATED AT 250 WORDS)

Reflex effects of prolonged cardiopulmonary baroreceptor unloading in humans

Most studies of the reflex responses to cardiopulmonary baroreceptor unloading with lower body negative pressure (LBNP) have assessed responses during the first few minutes of LBNP. It is unknown if these early changes are representative of the steady state. Thus we determined the response of heart rate, arterial pressure, forearm vascular resistance (FVR), and plasma norepinephrine (NE), renin (PRA), and aldosterone to prolonged (20 min) LBNP in nine normal subjects. All measurements were obtained at base line and after 3, 10, and 20 min of LBNP (-10, -20, and -40 mmHg). A 20-min recovery period was interposed between each period of LBNP. The heart rate and mean arterial pressure responses to LBNP during all levels of suction were not significantly different at 3, 10, and 20 min of continuous suction. Changes in FVR at 3, 10, and 20 min, respectively, were 18.4 +/- 3.2, 26.3 +/- 4.2, and 19.6 +/- 4.2 U during LBNP -10 mmHg; 33 +/- 7, 30.5 +/- 7.6, and 30 +/- 5.2 U during LBNP -20 mmHg; and 53.6 +/- 11.7, 57 +/- 8.8, and 49.4 +/- 12 during LBNP -40 mmHg, thus indicating a near maximal vasoconstrictor response at 3 min that was sustained throughout the 20 min during all levels of LBNP. Plasma NE rose to near peak level by 3 min. However, PRA and aldosterone changed significantly only after 20 min during LBNP at -10 and -20 mmHg. These data indicate that LBNP activates the sympathetic nervous system early, whereas activation of the renin-angiotensin-aldosterone axis is delayed. Our data should be taken into consideration in the design of future investigations of reflex neurohumoral responses to LBNP.