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PubMedDate not supplied

Combined assessment of left ventricular function and rest-redistribution regional myocardial thallium-201 activity for prognostic evaluation of patients with chronic coronary artery disease and left ventricular dysfunction.

BACKGROUND: This study evaluated the prognostic value of combined assessment of left ventricular (LV) function and regional myocardial thallium activity in patients with nonrecent myocardial infarction and LV dysfunction. METHODS AND RESULTS: Eighty-two patients with previous myocardial infarction (>8 weeks) and echocardiographic evidence of LV dysfunction underwent thallium-201 rest-redistribution tomography and cardiac catheterization. During the follow-up period (mean 25 months) there were 18 cardiac events (14 deaths and 4 nonfatal myocardial infarctions). Multivariate Cox regression analysis on clinical, angiographic, and thallium variables showed that the number of echocardiographic dysfunctional segments with preserved thallium uptake (> or =50% of peak activity; chi-square 11.03; p<0.005) and age (chi-square 8.12, p<0.01) were predictive of poor outcome. At incremental analysis, combined echocardiographic and thallium data provided significant additional information to clinical, thallium, and LV functional data, increasing global chi-square value from 22.4 to 31.5 (p< 0.01). Similarly, combined data gave additional information after considering clinical, echocardiographic, and LV functional data, increasing global chi-square from 17.8 to 22.3 (p <0.05). Differently, the number of diseased vessels at coronary angiography did not add further prognostic information. CONCLUSIONS: In patients with previous myocardial infarction and chronic LV dysfunction, the combination of echocardiographic and thallium rest-redistribution imaging data gives prognostic information incremental to those of clinical and LV functional data and to those of each technique considered separately.

Cardiac Catheterization↗

PubMed2004

Diastolic left ventricular function in preterm infants with a patent ductus arteriosus: a serial Doppler echocardiography study.

In very low birth weight neonates, a left-to-right shunt via persistent ductus arteriosus (PDA) may interact with diastolic left ventricular function, but specific changes of Doppler parameters have yet to be reported. In a serial transmitral Doppler study, we investigated the impact of a PDA on diastolic function parameters. Twenty-two patients with and without PDA were examined on day 3.8+/-1 and day 14+/-2 after birth. By the first examination, 13 out of 22 patients had a PDA; by the second examination, the number was still 8 out of 22. Peak early and atrial flow velocities (44.8+/-15 and 50.1+/-13 cm/s, respectively) were higher (p<0.05) for neonates with PDA compared to those with closed duct (30.9+/-6 and 34.2 cm/s, respectively). Isovolumic relaxation time (IVRT) was shorter in neonates with PDA (45+/-7 ms, N=21) compared to those with a closed duct (55.3+/-5 ms, N=23) (p<0.01). IVRT correlated inversely with cardiac index (R=-0.79, p<0.01). All observed changes reversed to the normal range after closure of the PDA. When premature infants with a PDA experience a preload challenge, early and atrial peak velocities increase and IVRT shortens significantly. This coincidence of elevated transvalvular pressure differences and decreased IVRT in neonates with immature diastolic function can best be explained as a result of left atrial pressure elevation. Consequently, pulmonary venous pressure must be elevated, with its inherent effect on pulmonary capillary physiology. Thus, the monitoring of left ventricular diastolic function adds significant information to the care of preterm infants with a PDA.

Blood Gas Analysis↗

PubMed2003

[Influence of the beta-blocker nebivolol on left ventricular function in patients with chronic heart failure].

BACKGROUND: Sympathetic activity is a significant predictor of a poor prognosis in heart failure. beta-blockers such as carvedilol, metoprolol or bisoprolol have been shown to improve the prognosis of patients with heart failure. AIM: This pilot study examined the tolerability and effect of the new beta-blocker nebivolol on left ventricular ejection fraction in patients with chronic heart failure. PATIENTS AND METHODS: Twelve patients with an ejection fraction of 13-39% were included into a double-blind, placebo-controlled, randomized trial with nebivolol on top of a standard therapy. Exercise time, heart rate, left ventricular function, and tolerability were examined at baseline and after 3 months of orally administered nebivolol (2.5 mg and 5 mg, n = 6) or placebo (n = 6). RESULTS: Nebivolol was well tolerated and NYHA stage improved in four patients. Heart rate decreased while the maximal exercise duration and performance remained stable. Left ventricular function improved (ejection fraction: increase from 29.8 +/- 10.66% to 41.2 +/- 10.53%; p = 0.007) after 12 weeks of nebivolol whereas placebo did not improve cardiac function statistically significant. Left ventricular endsystolic diameter decreased from 56.5 +/- 9.40 mm to 50.2 +/- 9.43 mm in the nebivolol group (p < or = 0.02). CONCLUSION: These data indicate that nebivolol might improve cardiac function in patients with chronic heart failure.

Administration, Oral↗

PubMed1993

Time course of left ventricular function and coronary patency after saruplase vs streptokinase in acute myocardial infarction. The PRIMI Trial Study Group.

As part of a prospective randomized double-blind trial (PRIMI) to study the early patency rate of the infarct-related artery after saruplase (INN for recombinant unglycosylated full-length human single-chain urokinase-type plasminogen activator) vs streptokinase in a subgroup of patients, left ventricular function was compared between both treatment groups at 90 min and 24 h after thrombolysis and at discharge, and ventricular function was related to the coronary perfusion grade. Despite a higher patency rate in the saruplase group 60 min after initiating thrombolysis, neither global ejection fraction nor hypokinesia at the infarct site were significantly different between the treatment groups at any of the three time points when function was measured. Hypokinesia at the infarct site remained almost equally severe throughout the study in patients with perfusion grade O, I, and II, and was consistently significantly milder in patients with perfusion grade III. In contrast, in patients with perfusion grade II there was a significant drop in hyperkinesia at the opposite wall at 24 h after thrombolysis and before discharge despite unchanged wall motion at the infarct site. Although patients treated with saruplase had a higher patency rate in the infarct related vessel shortly after the start of thrombolysis, no difference was found in left ventricular function compared to patients treated with streptokinase. Complete reperfusion (TIMI grade III) seems to be a prerequisite for left ventricular function recovery after thrombolysis, whereas only an occluded vessel (TIMI grade O and I) seems to be related to a longer lasting hyperkinesia at the opposite wall.

Double-Blind Method↗

PubMed1997

Ross procedure in congenital patients: results and left ventricular function.

METHODS: From April 1990 to August 1995, 121 patients (median age 42 years) underwent aortic valve replacement with allografts (69 patients) or autografts (52 patients). In this latter group, 24 Ross procedures have been performed in congenital patients since November 1991 (median age 10 years, range five months to 27 years): aortic incompetence (n = 17), isolated aortic stenosis (n = 5), small stenotic prosthesis (n = 2). Transthoracic echocardiography was obtained preoperatively in all patients and serially after surgery with the aim of measuring aortic and pulmonary annuli and evaluate gradients and incompetence and to study the left ventricular function. Intraoperative transoesophageal echocardiography was routinely used. Complete root replacement was performed in all patients. RESULTS: One patient died in the early postoperative period (4%). There was no late death. All survivors remained in NYHA class I and were free of complications and medications. No gradient nor any significant aortic incompetence could be demonstrated. In 17 patients with predominant aortic incompetence before surgery, the left ventricular function was followed prospectively, end-diastolic left ventricular dimensions diminished drastically from 2 +/- 3.4 S.D. above normal to -0.63 +/- 2.4 S.D. at one week postoperatively (day 10) to reach a normal value one to three months after surgery. Left ventricular mass remained abnormal at day 10 (from 4.7 +/- 3.3 S.D. to 5.3 +/- 3.8 S.D.) and diminished more progressively to reach a normal value (0.14 +/- 1.4 S.D.) at three months. This resulted in a significant decrease of end-systolic wall stress (-3.6 +/- 2.1 S.D.) and in a hyperdynamic function in the immediate postoperative days except in two patients. These two patients were characterized preoperatively by more severely dilated left ventricle (end diastolic dimension 5.3 +/- 0.03 versus 1.6 +/- 3 S.D.) with decreased left ventricular wall thickness (1.19 +/- 0.7 versus 3.44 +/- 1.9 S.D.), decreased ratio between end diastolic wall thickness and end diastolic dimension (0.14 +/- 0.06 versus 0.2 +/- 0.06) and a decreased velocity of shortening. Unlike the other 15 patients, the left ventricular function did not recover completely at mid term follow-up in those two patients. CONCLUSION: The Ross operation is a safe procedure and allows us to suppress completely the abnormal loading conditions of the left ventricle, resulting in a complete recovery of left ventricular function in most patients.

Adolescent↗

PubMed1991

Treatment of recurrent ischemia after thrombolysis and successful reperfusion for acute myocardial infarction: effect on in-hospital mortality and left ventricular function.

To determine the effect of treatment of recurrent ischemia after reperfusion for acute myocardial infarction on in-hospital mortality and left ventricular function recovery and to identify patients at highest risk of serious consequences in the event of recurrent ischemia in this setting, 405 consecutively treated patients were studied retrospectively. All patients received intravenous thrombolytic therapy within 6 h of ST segment elevation-documented infarction and had angiographic confirmation of their reperfusion status performed within 120 min of treatment. Three hundred three patients had successful reperfusion with or without rescue angioplasty and had no recurrent ischemia (group 1), 74 patients had initially successful reperfusion but subsequent recurrent ischemia (group 2) and 28 patients had failed reperfusion (group 3). The in-hospital mortality in groups 1 to 3 was 2.0%, 14.9% and 32.1%, respectively (p less than 0.001) and the change from baseline to prehospital discharge left ventricular ejection fraction was 1.2 +/- 9.3%, -0.8 +/- 8.7% and -4.3 +/- 5.3%, respectively (p = NS). Within the recurrent ischemia group (group 2), multiple regression analysis found absence of cardiogenic shock at presentation (p = 0.002) and successful treatment initiated within 90 min of recurrent ischemia (p = 0.045) to be the only variables independently correlated with in-hospital survival. Later successful reperfusion was not associated with improved hospital survival. The timing and success of treatment did not affect recovery of global or regional left ventricular function in the patients with paired angiographic studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMedDate not supplied

Evaluation of a Doppler-derived index combining systolic and diastolic left ventricular function in acute myocardial infarction.

Assessment of left ventricular (LV) function is crucial in the immediate postinfarction period. The authors evaluated the clinical applicability of the Doppler-derived myocardial performance index (MPI, defined as the sum of isovolumic contraction and relaxation times divided by LV ejection time) in patients with acute myocardial infarction (AMI) as to whether this index reflects the severity of LV dysfunction in this subgroup of patients. Post-AMI patients (n = 33) were compared with age- and sex-matched healthy subjects (n = 35). Within 24 hours of the AMI and 1 month thereafter, patients underwent 2D and Doppler echocardiography. Patients were divided into group A (Killip Class I, n = 22) and group B (Killip Class II-III, n = 11). The authors measured the LV ejection fraction (EF), diastolic indices (transmitral E and A waves, E/A ratio, deceleration time [DT], isovolumic contraction time [IVCT], isovolumic relaxation time [IVRT], MPI, LV end-systolic and end-diastolic volume indices [ESVi and EDVi] and wall motion score index [WMSi]). One-year mortality was also assessed. There was no significant difference concerning E and A waves, E/A ratio, and IVRT between the 2 groups. There were highly statistical differences at day 1 for EF (59.3 +/- 6.7% vs 36.8 +/- 4.5%, p<0.0001), DT (0.160 +/- 0.030 sec vs 0.127 +/- 0.022, p<0.005), MPI (0.344 +/- 0.084 vs 0.686 +/- 0.120, p<0.0001), ESVi (28.4 +/- 3.9 mL/m2 vs 46.2 +/- 8.4, p<0.001), and WMSi (1.58 +/- 0.06 vs 1.88 +/- 0.35, p=0.05), which persisted after 1 month. One-year mortality was significantly (0 vs 27.3%, p<0.01) lower in group A patients. This study shows that the MPI, reliably indicated LV dysfunction post-AMI, significantly correlated with clinically determined functional class, and possibly has some prognostic implication.

Case-Control Studies↗

PubMed1985

Alterations in left ventricular function, coronary hemodynamics and myocardial catecholamine balance with MDL 17043, a new inotropic vasodilator agent, in patients with severe heart failure.

To evaluate changes in myocardial energetics and systemic and cardiac sympathetic activity associated with improved left ventricular function after MDL 17043, a new inotropic vasodilator agent, systemic and coronary hemodynamics and myocardial catecholamine balance were determined in 17 patients with severe heart failure. After the administration of MDL 17043, cardiac index increased by 67% and pulmonary capillary wedge pressure decreased (25 +/- 5 to 14 +/- 7 mm Hg, p less than 0.01), indicating improved left ventricular function. Coronary sinus blood flow (75 +/- 29 to 111 +/- 51 ml/min, p less than 0.01) and myocardial oxygen consumption (9.9 +/- 3.3 to 11.8 +/- 5.4 ml/min, p less than 0.05) increased despite decreased myocardial oxygen extraction (11.7 +/- 2 to 10.1 +/- 3.3 vol%, p less than 0.05) and a higher coronary sinus oxygen content. Although transmyocardial lactate extraction remained unchanged, increased myocardial oxygen consumption has potential deleterious effects on myocardial metabolic function. Arterial norepinephrine concentrations and transmyocardial norepinephrine release also remained unchanged. These findings suggest that MDL 17043 improves left ventricular pump function, but produces no detectable change in systemic and cardiac sympathetic activity. Improved left ventricular function is associated with increased myocardial oxygen consumption despite primary coronary vasodilation.

Adult↗

PubMed1987

Monitoring effects of alpha-human atrial natriuretic polypeptide (alpha-hANP) on left ventricular function in patients with essential hypertension with a cardiac probe.

The effects of alpha-hANP on left ventricular function were studied with a cardiac probe in ten patients with essential hypertension. Our data showed that intravenous administration of alpha-hANP significantly elevated left ventricular function. At 5 min, the elevation of EF, RCO, ER, RSV, PFR were 13.23% (P less than 0.02), 12.7 (P less than 0.02), 0.618 (P less than 0.02), 0.133 (P less than 0.05), 0.283 (P less than 0.01), respectively. At 10 min, the increase of EF, ER, were 11.07% (P less than 0.02) and 0.233 (P less than 0.01), respectively. Atriopeptin significantly reduced systolic and diastolic blood pressure from 2 min to 20 min (P less than 0.001-0.05).

Adult↗

PubMed1992

Effect of chronic supraventricular tachycardia on left ventricular function and structure in newborn pigs.

OBJECTIVES: The purpose of this study was to examine the effects of supraventricular pacing tachycardia on left ventricular function and myocardial structure in newborn, immature pigs and to determine whether immature pigs respond to supraventricular tachycardia differently from adults. BACKGROUND: Previous studies have shown that supraventricular tachycardia causes dilated cardiomyopathy in adult animals; however, in humans, supraventricular tachycardia-induced congestive heart failure occurs most frequently in children and newborns. Because some clinical diseases may cause myocardial failure in adults but rarely do so in children, it was hypothesized that the effects of supraventricular tachycardia in newborns may be different from those in adults. METHODS: In two groups of newborn swine (3 weeks of age), left ventricular volume, mass and function were assessed with simultaneous echocardiography and cardiac catheterization and myocardial structure was examined with light and electron microscopy. Six piglets underwent 3 weeks of left atrial pacing tachycardia (240 beats/min) and six littermates served as a control group. Both groups were followed up for 3 weeks. RESULTS: At the end of the protocol, left ventricular dimensions increased in the piglets with supraventricular tachycardia compared with values in the control group, but there were no differences in left ventricular mass. Systolic function, assessed by fractional shortening, peak ejection rate and maximal rate of pressure development, was decreased in the group with supraventricular tachycardia. The fractional shortening-end-systolic stress relation in the piglets with supraventricular tachycardia decreased below normal values. Left ventricular diastolic function assessed by the relaxation time constant was prolonged, the peak filling rate was decreased and left ventricular stiffness was increased in the supraventricular tachycardia group. The morphologic data demonstrated that supraventricular tachycardia did not change total myocyte volume but did decrease total myofibrillar volume. CONCLUSIONS: Supraventricular tachycardia caused dilated cardiomyopathy in immature pigs. These changes in left ventricular function were associated with a decrease in cellular contractile proteins. Thus, the effects of supraventricular tachycardia on left ventricular function and structure in immature animals were comparable to previous findings in mature animals.

Age Factors↗

PubMed1993

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) decrease in diastolic left ventricular function assessed by echocardiography.

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) are known to be associated with cardiomyopathy. Systolic and diastolic left ventricular functions were assessed by M-mode and Doppler echocardiography in four patients with MELAS and in 14 normal controls. The interventricular septal thickness and left ventricular posterior wall thickness were greater (11.0 +/- 1.6 mm vs. 5.8 +/- 0.7 mm and 11.0 +/- 2.2 mm vs. 5.9 +/- 0.8 mm) in patients with MELAS than in a control group. Parameters of systolic left ventricular functions (ejection fraction, shortening fraction, systolic time intervals, and mean Vcf) and left ventricular dimensions were not significantly different between the two groups. To assess the diastolic function, blood flow velocity across the mitral valve was measured by Doppler echocardiography and various indexes were obtained. In patients with MELAS, the impairment of diastolic left ventricular filling was demonstrated by decrease in the following indexes: peak flow velocity in the early passive filling period (E) (0.76 +/- 0.10 m/s vs. 0.94 +/- 0.09 m/s), integrated velocity for total E (10.2 +/- 1.3 vs. 13.0 +/- 0.9), the ratio of E and late atrial filling integrated velocities (1.72 +/- 0.06 vs. 2.49 +/- 0.29).

Adolescent↗

PubMed1994

Comparative observation on effect of electric acupuncture of neiguan (P 6) at chen time versus xu time on left ventricular function in patients with coronary heart disease.

Paired experimental design was adopted in this experiment for comparative observation on effect of electric acupuncture (EA) of Neiguan (P 6) at Chen Time (7 a.m. to 9 a.m.) versus Xu Time (7 p.m. to 9 p.m.) on left ventricular function in patients with coronary heart disease (CHD). The results show that EA performed at Chen Time could improve the left ventricular function of CHD patients as indicated by shortening of PEPI and decrease of PEPI/LVETI ratio; on the contrary, EA performed at Xu Time prolonged PEPI and raised PEPI/LVETI ratio in CHD patients, suggesting impairment of left ventricular function.

Acupuncture Points↗

PubMed1995

[Effects of Astragalus membranaceus on left ventricular function and oxygen free radical in acute myocardial infarction patients and mechanism of its cardiotonic action].

Dynamic observations for 4 weeks were made on left ventricular function and oxygen free radical (OFR) in 43 patients first suffering from acute myocardial infarction and hospitalized in Coronary Care Unit with an attack less than 36 hours. The results showed that the Astragalus membranaceus (AM) could strengthen the left ventricular function and had an effect of anti-OFR. After administration of AM, the ratio of pre-ejection period/left ventricular ejection time (PEP/LVET) was decreased, the superoxide dismutase (SOD) activity of red blood cell was increased, and the lipid peroxidation (LPO) content of plasma was reduced. There was a significant difference between the AM group and the control group in the parameters above-mentioned. The study demonstrated that the PEP/LVET ratio was closely correlated with the SOD and LPO. It suggested that the anti-OFR effect of AM was one of the mechanisms of its cardiotonic action.

Adult↗

PubMed1992

Myocardial dysfunction in silent myocardial ischemia as demonstrated by ambulatory radionuclide left ventricular function studies.

Until recently, it has not been possible to combine both ambulatory electrocardiographic monitoring, monitoring and ambulatory left ventricular function monitoring, but new developments have helped solve this problem. A technique based on the nuclear probe was introduced in the early 1980s to allow continuous recording of left ventricular volumes and ejection fraction over a 4 to 6 hour period during ambulatory activities following a single injection of radioisotope; the device was termed the VEST. In addition to validation studies, left ventricular function during ambulatory activities of various types has been measured with the VEST, and there are now several reports that document reduction in left ventricular ejection fraction in patients with coronary artery disease. These episodes meet the criteria for silent ischemia: objective evidence of myocardial ischemia in the absence of angina or anginal equivalents. Thus, patients with coronary artery disease can be followed for hemodynamic evidence of myocardial ischemia (even when they are not aware of the episodes) and results of therapy better monitored than by the ambulatory ECG alone.

Coronary Disease↗

PubMed1992

Effect of propranolol and disopyramide on left ventricular function at rest and during exercise in hypertrophic cardiomyopathy.

In 19 patients with hypertrophic cardiomyopathy (15 males, 4 females, mean age 49.2 +/- 10.8 years) left ventricular function was studied with radionuclide ventriculography at rest and during exercise in a crossover design without intervention and after disopyramide and propranolol treatment. 15 of the 19 patients had a resting or latent intraventricular gradient of more than 30 mm Hg. Left ventricular function at rest and during exercise was evaluated before medication, 90 min after oral administration of 200 mg disopyramide or 160 mg propranolol and after 3 weeks of oral therapy with disopyramide 200 mg 2 times a day or propranolol 80 mg 4 times a day. After long-term treatment with disopyramide, resting ejection fraction decreased from 72 +/- 12 to 69 +/- 14% (p less than 0.01) and peak ejection rate (PER) decreased from 3.46 +/- 135 to 3.24 +/- 65 end-diastolic volume (EDV).s-1 (p less than 0.01). Peak filling rate (PFR) at rest decreased from 3.01 +/- 0.8 to 2.77 +/- 0.63 EDV.s-1 (p less than 0.05). Time to peak filling rate (TPFR) at rest and during exercise after acute and chronic therapy did not change compared to control values. Acute and long-term administration of propranolol lead to a significant reduction in heart rate at rest and during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1991

Hemodynamic study of intravenous propionyl-L-carnitine in patients with ischemic heart disease and normal left ventricular function.

Propionyl-L-carnitine was given intravenously to ten patients with chronic ischemic heart disease who had normal left ventricular function and had not had a previous myocardial infarction. Subsequently, pulmonary and systemic circulation, left ventricular function, and the relationship between the ventricle and afterload were evaluated. This drug, at a dose of 15 mg/kg, improves ventricular function by easing the load and by enhancing cardiac efficiency. The ejection impedance is reduced with a consequent increase in stroke volume as a result of a) a decrease in systemic and pulmonary resistance and b) an increase in arterial compliance. Arterial pressure is maintained due to an increase in total external heart power. Since the tension time index shows a proportionally smaller increase in the energy requirement, it follows that cardiac efficiency has been improved and ventricle-afterload matching is optimal. These results suggest but do not prove that propionyl-L-carnitine exhibits a positive inotropic property.

Adult↗

PubMed1982

Left ventricular function in hypothyroidism. Responses to exercise and beta adrenoceptor blockade.

The effects of exercise and beta adrenoceptor blockade on left ventricular function were assessed in eight patients with hypothyroidism before and during thyroxine replacement treatment. Left ventricular ejection fraction, measured by radionuclide ventriculography, was reduced in hypothyroid patients at rest and on exercise. The rise in ejection fraction with exercise was, however, similar in both groups. Pretreatment with intravenous propranolol reduced the ejection fraction at rest 9% in both hypothyroid and euthyroid patients and reduced the rise on exercise. Directional changes in a second index of myocardial contractility based on the shape of the ventricular volume curve paralleled the changes in the ejection fraction. Left ventricular function is therefore reversibly depressed by thyroid hormone deficiency but responses to exercise and beta adrenoceptor blockade are normal. There is no evidence of altered adrenergic sensitivity in the control of myocardial contractility in hypothyroidism.

Adult↗

PubMed2005

Reduced left ventricular functional reserve in hypertensive patients with preserved function at rest.

In many hypertensive patients, left ventricular pump function is normal at rest but abnormal during exercise. Myocardial dysfunction or altered left ventricular loading may be responsible for this finding. To verify the hypothesis of impaired myocardial functional reserve in the hypertensive heart, we assessed the response of stress-adjusted midwall shortening to graded, low-dose dobutamine infusion in hypertensive subjects with normal midwall shortening at rest. Sixty-five subjects (45 never treated hypertensive subjects and 20 normotensive volunteers comparable for age) received dobutamine at 1, 2, 3, 4, and 5 microg x kg(-1) x min(-1) for 5-minute steps; within this range of infusion rates, heart rate and systemic blood pressure were stable. Two-dimensional, M-mode, and Doppler echocardiography were performed at baseline and at the end of each step. In normotensive controls, midwall shortening increased from baseline during 2 microg x kg(-1) x min(-1) dobutamine by an average of 16+/-4.5% (P<0.01); a value of 2 standard deviations below this mean response was taken as the lower limit of normal. In the hypertensive subjects, 24 had a normal midwall shortening response to dobutamine at this dose (group I) and 21 had a subnormal response (group II). Whereas blood pressure and left ventricular mass were similar in group II and group I, the former had greater relative wall thickness (P<0.01) than the latter. beta-adrenergic stimulation by very-low-dose dobutamine unmasks subtle impairment of myocardial functional reserve in hypertensive subjects with normal myocardial performance at rest. This alteration seems to be related mainly to increase in left ventricular relative wall thickness.

Adrenergic beta-Agonists↗