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PubMed1988

Elevated coronary sinus pressure does not alter myocardial blood flow or left ventricular contractile function in mature sheep. Implications after the Fontan operation.

The hypothesis that elevation of coronary sinus pressure affects coronary blood flow and ventricular function was tested in this study of seven adult ewes placed under pentobarbital anesthesia. Coronary sinus pressure was elevated by partial balloon occlusion. Right atrial, left atrial, and aortic mean pressures and rate of rise of left ventricular pressure were measured. Coronary blood flow was determined with radioactive microspheres. Studies were performed at control and at moderate (15 to 20 mm Hg) and marked (30 to 35 mm Hg) elevation of coronary sinus mean pressures. Despite increase of coronary sinus pressure from a control value of 2 mm Hg +/- 1 to levels of 19 mm Hg +/- 1 and 34 mm Hg +/- 1, no significant changes were observed in right atrial, left atrial, or aortic mean pressure or rate of rise of left ventricular pressure. Both endocardial and epicardial blood flows were unaffected. The endocardial/epicardial flow ratio at moderate coronary sinus pressure elevation was significantly increased, which suggested local subendocardial vasodilation in the absence of changes in transmural perfusion. The findings suggest that isolated increase in coronary sinus pressure is not a major determinant of myocardial blood flow or ventricular performance in the normal ewe.

Animals↗
PubMed1983

[The value of temporary electrosystolic pacing for treating low output in posterior necrosis with adiastole].

Early catheterisation was performed in 27 patients with an acute inferior myocardial infarction less than 3 days old complicated by signs of low output with right ventricular dysfunction. All patients had hemodynamic criteria of adiastole (PCP = 14.9 +/- 31 mmHg and LVEDP = 14.1 +/- 4.7 mmHg) with low cardiac output (CI = 1.41 +/- 0.32 l/min/m2). An atropine resistant bradycardia was characteristic (HR = 65 +/- 17.2/min) due to advanced or complete AV block (11 cases), sinoatrial block (3 cases, one with right atrial standstill) or sinus/parasinus rhythm (13 cases) inappropriate to the severity of their hemodynamic state. Although the prognosis based on the discriminating linear function FI = -0.427 + 0.00121 LVW - 0.00125 TPR was initially poor and predicted the death of 21 out of the 27 patients at one month, the outcome was usually favourable and only 8 patients died during the first month. Fifteen patients were treated by temporary endocavitary RV pacing. As the heart rate was increased from 53.8 +/- 11.2 to 92.4 +/- 4.9/min, the CI rose from 1.35 +/- 0.26 to 1.85 +/- 0.46 l/min/m2 (p less than 0.001) with a fall in SI from 26.7 +/- 8.3 to 20.1 +/- 5.6 ml/beat/m2 (p less than 0.005). The results were even further improved in 3 cases by sequential A-V pacing. The observed hemodynamic improvement continued during the period of pacing providing volumic expansion maintained LVEDP above 10 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1993

[Hemodynamic variable analysis in patients with systemic arterial hypertension undergoing physical exercise].

PURPOSE: To verify the exercise-induced hemodynamic changes in moderate hypertensive patients. METHODS: Twenty nine patients were studied and they were submitted to cycloergometer supine exercise (50w and 100w) during cardiac catheterization. The hemodynamic variables were measured: cardiac index (CI), stroke volume (SV), systemic arterial resistance (SAR), pulmonary arterial resistance (PAR), wedge pressure (WP), right atrial pressure (RA), systolic arterial pressure (SP), diastolic arterial pressure (DP), mean arterial pressure (MP) and heart rate (HR). To evaluate the cardiac function, the patients were divided in two groups: GI with CI > 2.5 ml/min/m2 and GII CI < 2.5 ml/min/m2. RESULTS: During exercise, patients from GI and GII were similar-according to MAP, RA, WP, and HR. On the other hand, GI and GII exhibited different (#) behavior regarding SV, PAR and SAR. During the three exercise conditions, rest (R), 50w and 100w it was observed: a) PAR-R = 50 = 100 (GI); b) MP, PAR, WP, SV, SAR-R #50 #100 (GI); c) HR, PAR and SAR-R #50 #100 (GII). There was no correlation between the cardiac function (CI, SV) and the circulatory adjustment (PAR and SAR) or the pressure curve (SP, DP, MP) and HR. CONCLUSION: The results suggest that the cardiac function of GI patients depends, mainly, on the inotropism, while in GII patients it depends on the decrease of the afterload (PAR and SAR). Those changes may appear even in the late exercise stage (100w), with a bias to attain the GI levels. Those observations suggest functional changes in vasomotor tone of GII patients.

Adult↗
PubMedDate not supplied

Immediate cardiac allograft failure. ECMO versus total artificial heart support.

Optimal support for immediate cardiac allograft failure is unknown. With the introduction of heparin bonded extracorporeal membrane oxygenated circuits, prolonged cardiopulmonary support is possible. The authors report a case that involved 2 days of right atrial to ascending aorta extracorporeal membrane oxygenated support after immediate donor organ failure prevented the patient from exiting bypass. Continued deterioration in cardiac function led to an attempt at conversion to a total artificial heart as a bridge to retransplant. However, this procedure resulted in transbronchial exsanguination and recipient death. The autopsy showed pulmonary thrombosis with infarction and hemorrhage. The authors recommend caution in the use of extracorporeal membrane oxygenated support for patients with immediate and profound graft failure because of the increased risk of stasis thrombosis and pulmonary infarction due to sluggish pulmonary and left atrial blood flow. Instead, institution of total artificial heart or biventricular support may be preferable as the risks of thrombus and infarction are less.

Adolescent↗
PubMed1992

Determinants of left ventricular filling dynamics: alteration in the Doppler-derived transmitral filling profile with progressive impairment of cardiac function in a dog preparation.

To clarify the factors determining transmitral filling, left ventricular and atrial pressures (LVP and LAP) and Doppler-derived diastolic indices were analysed in six anaesthetized dogs at various right atrial pacing rates during dextran infusion. The relationship of the late to early diastolic peak velocity ratio (A/E ratio) to end-diastolic LVP (LVEDP) showed a quadratic curve concave to the LVEDP axis in five animals (r2 = 0.320-0.588). An elevation in LVEDP up to 25 mmHg accompanied an increase in A/E ratio (ascending limb), and further LVEDP elevation caused its inverse decline (descending limb). Multiple regression analysis indicated that A/E ratio correlated positively with maximal LVP, a-wave LAP and heart rate, and negatively with v-wave LAP in both limbs. The time constant of isovolumic LVP decline, which was prolonged as LVEDP was elevated, was a positive correlate of A/E ratio in the ascending limb, but lost its influence on A/E ratio in the descending limb. An elevation in v-wave LAP must have masked the expected effect of left ventricular relaxation abnormality on A/E ratio in this limb. Thus, the transmitral filling profile did not alter unidirectionally, but returned to that seen before volume loading, with a simultaneous progressive impairment of cardiac function.

Animals↗
PubMed1998

Conversion of the atriopulmonary Fontan connection to a total cavopulmonary connection.

Right atrial-to-pulmonary artery anastomosis (modified Fontan-Kreutzer operation) often results in substantial enlargement of the right atrium over time. Massive right atrial dilatation can cause loss of laminar flow, stasis, compression of the right pulmonary veins posteriorly, and leftward shift of the atrial septum. Some patients may develop arrhythmias related to atrial distension and multiple suture lines. Chronic elevation of the central venous pressure may cause liver dysfunction and/or protein-losing enteropathy in some patients. Some patients with atriopulmonary Fontan connections who develop a decline in functional status may benefit from conversion to a total cavopulmonary connection. Patients with significant ventricular dysfunction can usually only be treated by cardiac transplantation. However, other problems may be successfully managed by revision of the atriopulmonary Fontan connection to a total cavopulmonary anastomosis. Conversion to a total cavopulmonary connection should improve cardiac output by restoring laminar flow, by relieving compression of the right pulmonary veins, and by alleviating the leftward displacement of the atrial septum. Copyright 1998 by W.B. Saunders Company

Journal Article↗
PubMed2006

Alterations in contractile protein composition and function in human atrial dilatation and atrial fibrillation.

The cellular mechanisms responsible for contractile dysfunction associated with atrial fibrillation (AF) are still poorly understood. Atrial fibrillation is often preceded by atrial dilatation. This study aimed to explain contractile alterations associated with AF and their relation to atrial dilatation, by studying the relationships between atrial dimensions, contractile protein composition, force production and Ca(2+)-sensitivity. Force development was determined in mechanically isolated single skinned cardiomyocytes from right atrial appendages from patients with sinus rhythm without (SR;n=9), or with atrial dilation (SR+AD;n=11) or atrial fibrillation (AF;n=16). Echocardiography showed that, compared to the SR group, mean right atrial dimensions were increased by 18% and 35% in the SR+AD and AF group, respectively (P<0.05). Protein composition was determined by 1- and 2-dimensional gel electrophoresis. Compared to the SR group, the AF group exhibited: a reduction in the kinetics of force redevelopment (K(tr)) in isolated atrial cardiomyocytes, enhanced protein expression of the slow myosin heavy chain isoform (beta-MHC), an increase in troponin T (TnT) phosphorylation and a marked increase (70%) of the cytoskeletal protein desmin. Significant correlations were observed between the right atrial major axis (RA(major)) and beta-MHC expression as well as the desmin/actin ratio. Our findings indicate that dilatation may influence cardiomyocyte stability through altered desmin expression, but that it does not predispose to the alterations in contractile function observed in AF.

Aged↗
PubMed1998

Short-term hemodynamic effects of DDD pacing from ventricular apex, right ventricular outflow tract and proximal septum.

Recently, short-term hemodynamic benefits of right ventricular outflow tract (RVOT) or proximal septum (His bundle area) pacing have been reported in comparison with traditional apical stimulation in preliminary investigations. The purpose of the present study was to compare the hemodynamics obtained during DDD pacing from ventricular apex, RVOT and proximal septum in patients with normal left ventricular function. A simultaneous hemodynamic and Doppler-echocardiographic study was performed in 21 patients (age 67 +/- 7 years) with sick-sinus syndrome (8 pts) or 2nd-3rd degree atrioventricular (AV) block (13 pts). The three stimulation sites were randomized and pacing was applied at an identical rate (84 +/- 5 beats/min) and at a constant AV delay (150 ms). Electrocardiographic, hemodynamic and Doppler-echocardiographic investigations were performed during stimulation from each site. The QRS duration did not show significant differences during DDD pacing from ventricular apex, RVOT and proximal septum. The hemodynamic measurements (systemic pressures, mean pulmonary wedge pressure, pulmonary pressures, right ventricular end-diastolic pressure, mean right atrial pressure, cardiac index, systemic vascular resistance and arteriovenous O2 difference) did not show significant differences during pacing from the three sites. Moreover, no significant differences were observed for the Doppler-echocardiographic measurements of systolic function (aortic stroke distance, left ventricular ejection fraction) and diastolic function (isovolumetric relaxion time, mitral E/A ratio, deceleration rate of the E wave). The results suggest that in patients with normal left ventricular function DDD pacing from RVOT or proximal septum does not improve cardiac function with regard to apical pacing.

Aged↗
PubMed1989

Alterations of coronary blood flow and reserve with aging in Fischer 344 rats.

To determine whether aging affects the coronary circulation, left and right ventricular coronary blood flow and vascular resistance at rest and after maximal vasodilation were measured by left atrial injection of radioactive microspheres in conscious, unrestrained male Fischer 344 rats at 4, 12, and 20 mo of age. As a function of age, maximal coronary blood flow per 100 g of tissue decreased by 43% in the left ventricle at both 12 and 20 mo, whereas a 44 and a 47% reduction was found in the right side of the heart at the same time intervals. Minimal coronary vascular resistance per 100 g of myocardium increased by 56 and 36% in the left ventricle and by 48 and 44% in the right at 12 and 20 mo, respectively. No change was found in total minimal coronary resistance for either ventricle despite an increase in myocardial mass. Maximal coronary blood flow per 100 g to the endocardium was depressed more than epicardial flow, leading to a 24% reduction in the endocardial-to-epicardial flow ratio at 20 mo. Coronary vascular reserve per 100 g, expressed as the increase in coronary blood flow during maximal coronary vasodilation, was greater in the right than in the left ventricle at all ages. It is concluded that the changes in coronary hemodynamics associated with maturation and aging are comparable with those seen in pressure overload hypertrophy with an increased vulnerability potential of the myocardium to ischemic episodes, particularly of the subendocardial region of the left ventricle.

Aging↗
PubMed1991

Catheter ablation of left posteroseptal accessory pathways and of long RP' tachycardias with a right endocardial approach.

Fifty-four patients with a posteroseptal accessory connection and symptomatic tachycardias underwent catheter ablation of the anomalous pathway. Eight had the permanent form of reciprocating tachycardias (long RP' tachycardia) and 46 had a left posteroseptal preexcitation marked by a prominent R wave in lead VI. In 14 of 19 patients, ventriculoatrial conduction time during tachycardia lengthened in conjunction with functional left bundle branch block; this behaviour was significantly different from a series of patients with right posteroseptal preexcitation in which functional left bundle branch block lengthened the ventriculoatrial time in only one of 12 patients. A quadripolar electrode catheter was left within the proximal coronary sinus in order to locate the earliest atrial or ventricular activation site. The appropriate bipole was used as the radiographic and electrophysiological reference of the insertion of the accessory pathway. A catheter was then positioned on the septal side of the right atrium, outside the coronary sinus, so that atrial activity during reciprocating tachycardia and ventricular activity during preexcitation were synchronous with or earlier than that recorded within the proximal coronary sinus. Accessory pathway potential was not recorded in any patient. Early ventricular potential occurring --1.5 +/- 8 ms relative to delta wave onset was present at that site. In 38 patients, including 5 with permanent junctional tachycardia, high current (14 mA) pacing yielded direct ventricular paced QRS complexes (no delay spike-QRS) with a morphology similar to left posteroseptal maximal preexcitation. Slight movements of catheter position yielded significantly different pace-maps. One to eight 160 J cathodal shocks (510 +/- 213 J cumulative per patient) were delivered at this site in 61 sessions. Following fulguration, tachycardia recurred without drugs in only one patient over a follow-up period of 20 +/- 13 months. Asymptomatic intermittent preexcitation recurred in two patients. In all patients with long RP' tachycardia, the ablation procedure was successful without the need for drugs or permanent cardiac pacing. A long-term follow-up electrophysiological study in 18 patients demonstrated that conduction through the anomalous pathway was absent in 16 and deeply altered in the two patients with intermittent preexcitation; no tachycardia was inducible in any patient. In conclusion, catheter ablation of left posteroseptal accessory pathways is a feasible procedure using a right atrial approach outside the coronary sinus. This technique is also effective for the treatment of the permanent form of reciprocating tachycardia.

Adolescent↗
PubMed1989

Acute effects of intravenous UD-CG 115 BS (pimobendan) on the cardiovascular system and left ventricular pump function.

Acute hemodynamic effects of 5 and 10 mg i.v. UD-CG 115 BS (pimobendan) were studied by right and left heart catheterization in idiopathic dilated cardiomyopathy (NYHA classes II and III; 5 mg = group I, n = 6; 10 mg = group II, n = 6). Effects on left ventricular function were evaluated by left ventricular angiograms and measurement of left ventricular dp/dtmax before and 2.5 h after administration of UD-CG 115 BS. Right atrial pressure (RAP), pulmonary capillary wedge pressure (PCP), cardiac output (CO), heart rate (HR), and systemic blood pressure (BP) were assessed before and 2.5, 4, and 6 h after administration of UD-CG 115 BS. PCP was maximally reduced by 10 mg of UD-CG 115 BS from 18.3 +/- 6.2 to 6.2 +/- 3.4 mm Hg (p less than 0.005) and by 5 mg from 12.2 +/- 7.5 to 8.3 +/- 7.1 mm Hg (p less than 0.05). Maximum reduction of RAP was significant only in group II (p less than 0.05). CO increased in a similar way after both doses (group I: from 5.5 +/- 1.9 to 7.8 +/- 1.3 L/min, p less than 0.005; group II: from 5.0 +/- 1.3 to 7.5 +/- 1.8 L/min, p less than 0.05). Mean arterial blood pressure was slightly reduced only by 10 mg of UD-CG 115 BS. Heart rate rose from 84 +/- 11 to 100 +/- 14 beats/min in group I (p less than 0.05), whereas after 10 mg no change in heart rate was noted. Left ventricular end-diastolic (EDVI) and end-systolic volume (ESVI) indices were clearly reduced by both 5 and 10 mg of UD-CG 115 BS.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathy, Dilated↗
PubMed1987

[Echocardiographic characteristics and clinical significance of the spontaneous contrast echoes].

Spontaneous echocardiographic contrast is caused by increased ultrasonic density in the cardiac chambers or great vessels, or both, with the characteristic flow pattern of blood, but in the absence of any intravascular injections. This study demonstrated the clinical features and characteristics of the echocardiographic findings of eight patients with spontaneous contrast echoes. Spontaneous contrast echoes were observed in the right heart in five patients, and in the left heart in two. In one patient spontaneous contrast echoes were observed in the right and left heart. All six patients with spontaneous contrast echoes in the right heart had impaired liver function. In these patients, we observed that spontaneous contrast reaching the heart via the hepatic vein on two-dimensional echocardiography. In one patient with atrial septal defect, these contrast echoes were also recognized in the superior mesenteric vein and portal vein. Since capillary beds normally remove ultrasound contrast, the failure of this function suggests porta-systemic shunting in or around the liver. All three patients with spontaneous contrast echoes in the left heart had prosthetic valve dysfunction including paravalvular or transvalvular regurgitation, and consequent hemolysis. Under these conditions, water-vapor bubbles may be formed because of an exhaust pressure decrease due to the Bernoulli effect, or gases may be released from erythrocytes during hemolysis. These water-vapor bubbles or gases could be the cause of spontaneous contrast echoes in the left heart. In conclusion, spontaneous contrast echoes in the right heart are produced by gas absorbed from the intestine because of porta-systemic shunting. The cause of spontaneous left-sided heart echo contrast may be related to prosthetic valve regurgitation, and consequently to hemolysis.

Adult↗
PubMed1981

Augmentation of pulmonary blood flow after right ventricular bypass.

We have studied pulmonary hemodynamics after right ventricular bypass in dogs. Manipulations of pulmonary vascular resistance and transpulmonary blood pressure difference (delta Pp) made it possible to increase pulmonary blood flow. Decreasing resistance by raising arterial pH from 7.25 to 7.38 increased flow by 24.9%. Infusion of homologous blood to increase right atrial pressure from 10 to 30 mm Hg lowered resistance 41.5% and raised flow 183%. Left ventricular bypass (left atrium to aorta) lowered left atrial pressure, increased arteriovenous pressure gradient by 41.4%, and raised flow 32.8%. These experiments support earlier clinical observations of the importance of low pulmonary vascular resistance and of good left ventricular function both in selection of patients and in postoperative management after right ventricular bypass. Attention to the principles we discuss may permit right ventricular bypass operation in some patients who would not be operable by current criteria.

Animals↗
PubMed2004

Improved early results with the Fontan operation in adults with functional single ventricle.

BACKGROUND: A growing number of adults with functional single ventricles are presenting as candidates for first-time and redo-Fontan operations. This study describes the clinical presentation and early operative results of adults who have undergone Fontan modifications. METHODS: Between July 1995 and April 2003, 23 patients (>18 years old) had Fontan operations. We retrospectively reviewed their perioperative courses. RESULTS: Twenty-three Fontan operations (first-time [n = 8] and redo [n = 15]) were performed with no early or late deaths. No patient has required reoperation. One patient has been listed for orthotopic heart transplantation. The overall mean age is 23 years (18 to 41 years); mean follow-up, 30 months; median postoperative hospital stay, 8 days (4 to 34 days); and median duration of chest tube drainage, 4 days (2 to 12 days). The postoperative New York Heart Association (NYHA) functional class was improved in 22 of 23 patients. Eight first-time Fontan operations (7 of 8 nonfenestrated) were performed; lateral tunnel (n = 7) and extracardiac conduit (n = 1). Two patients had preoperative arrhythmias. New onset arrhythmias (ventricular tachycardia and sinus node dysfunction), requiring treatment, occurred in two patients. Fifteen redo-Fontan operations (all nonfenestrated) were performed; lateral tunnel (n = 5) and extracardiac conduit (n = 10). Fifteen patients had preoperative arrhythmias, thirteen of which had intraatrial reentry tachycardia (IART) and required antiarrhythmic medications. Concomitant intraoperative radiofrequency ablation (RFA) (n = 11) and cryoablation (n = 1) procedures were performed. In the immediate postoperative period, there was IART recurrence in five patients (post-RFA [n = 4] and postcryoablation [n = 1]). At latest follow-up, no patient is being treated with antiarrhythmic medications. Two patients had new onset atrial arrhythmias that required treatment. CONCLUSIONS: The Fontan operation can be performed in adults with minimal morbidity and improved NYHA functional class. New onset arrhythmias requiring treatment are sources of perioperative morbidity. Complete arrhythmia resolution of the preoperative arrhythmia may not be achieved in the immediate postoperative period in redo-Fontan patients. However, modification (intraoperative radiofrequency ablation-right atrial debulking) of the atrial tachycardia circuits in the redo-Fontan patients can result in complete resolution of preoperative atrial tachyarrhythmias at early follow-up.

Adolescent↗
PubMed1991

Characteristics of serial electrocardiograms in heart transplant recipients.

To characterize "normal electrocardiogram patterns" after transplantation, serial surface 12-lead electrocardiograms (ECGs) taken 2 weeks, 1 month, and 1 year postoperatively in a group of 50 heart transplant recipients were analyzed and were correlated with clinical parameters. Some recipient atrial activity was evident in 40% of patients at 2 weeks, but in only 16% at 1 year; donor atrial activity was normal in 90% to 94% of patients at all times. ECG intervals generally were normal and did not change over time. The most prevalent abnormality was the presence of incomplete (IRBBB) or complete right bundle branch block (RBBB) patterns (14% at 2 weeks, 16% at 1 month, and 22% at 1 year). In patients with hemodynamic measurements available approximately at the time of the ECG recording 1 year following transplantation, there was a significant correlation between the presence of IRBBB and RBBB patterns and somewhat higher levels of right atrial mean pressure (6.8 versus 3.9 mm Hg, p = 0.01), pulmonary artery systolic pressure (32.5 versus 24.5 mm Hg, p = 0.001) and diastolic pressure (16.2 versus 11.2 mm Hg, p = 0.004), and right ventricular systolic pressure (31.4 versus 26.9 mm Hg, p = 0.019) and pulmonary artery wedge mean pressure (11.3 versus 7.9 mm Hg, p = 0.010). Repolarization changes were also common but decreased in frequency over time (78% at 2 weeks to 34% at 1 year) and did not correlate with the presence or absence of rejection. We conclude that ECG abnormalities in heart transplant recipients are generally mild and that IRBBB and RBBB patterns correlate with increased right heart pressures.

Atrial Function↗
PubMed1991

Effects of aprindine on monophasic action potentials.

Using a catheter electrode developed by the authors for recording monophasic action potentials (MAPs), the atrial and ventricular MAPs of seven mongrel dogs were simultaneously recorded. The results were used to evaluate the effect of the new antiarrhythmic drug aprindine on MAPs. An electrophysiologic study was also carried out to evaluate the effect of aprindine on the conduction system. Aprindine caused a significant increase in both the AH interval (at a basic cycle length of 400 ms) and the HV interval (at basic cycle lengths of 400 and 500 ms). The effective refractory period increased in both the right atrium and the right ventricle. Although an increase in MAP duration at repolarizations to 90% MAP (MAPD90) was not observed in the right atrium, a significant increase was noted in MAPD90 in the right ventricle. There were no significant changes in the ratio between the effective refractory period and MAPD90 of the right ventricle before and after administration of aprindine. This result suggests that increases in MAPD90 contribute to an increase in the effective refractory period of the right ventricle.

Action Potentials↗
PubMed1986

Calcitonin gene-related peptide as potential neurotransmitter in guinea pig right atrium.

The potential neurotransmitter role of calcitonin gene-related peptide (CGRP) in cardioacceleratory nonadrenergic noncholinergic (NANC) nerves was examined in the guinea pig right atrium in vitro. In the presence of atropine, a muscarinic antagonist, and atenolol, a beta-adrenoceptor antagonist, transmural nerve stimulation (TNS) of the isolated right atrium caused a positive chronotropic response, which is slow in both onset and decay. This TNS-induced slow response was assumed to be mediated by NANC nerves in the right atrium since tetrodotoxin inhibited the response. Dense distribution of CGRP-like immunoreactive (CGRP-I) nerves was demonstrated in the sinus node. Exogenously applied CGRP exerted a positive chronotropic effect on the isolated right atrium in a dose-dependent manner. Both CGRP-I nerves and NANC response induced by TNS were not affected by surgical sympathectomy and reserpine pretreatment but were abolished by the pretreatment of animals with capsaicin. The results suggest that CGRP is the neurotransmitter of cardioacceleratory NANC nerves in the right atrium of the guinea pig.

Animals↗