ABSTRACT
Patients with cardiac disorders have defective parasympathetic control of heart rate. To evaluate the possibility of similar changes in sympathetic control of heart rate, we compared reflex chronotropic responses to 80 degree upright tilt and nitroglycerin-induced hypotension in 31 cardiac patients and 7 normal individuals before and after partial parasympathetic blockade with atropine. Tilting revealed an attenuation of the normal heart rate increase in patients; the magnitude of this defect was greatest in patients with more severe symptoms (class III) and evidence of left ventricular dysfunction (the heart rate increase averaged 25 plus or minus 3 beats/min in normal subjects, 12 plus or minus 2 beats/min in class I-II patients, and 7 plus or minus 1 beats/min in class III patients). Class III symptoms due to mechanical causes (mitral stenosis), however, were not associated with this defect. A marked reduction in heart rate rise with hypotension was seen only in those class III patients without mitral stenosis (0.4 plus or minus 0.1 beats min-minus 1 mm Hg-minus 1 vs. 3.0 plus or minus 0.5 beats min-minus 1 mm Hg-minus 1 in normal subjects). This abnormality also persisted after atropine administration, thus confirming a defect in the sympathetic as well as the parasympathetic component of baroreceptor-mediated reflex heart rate control in patients with cardiac dysfunction. Infusions of isoproterenol produced equivalent rises in heart rate in patients and normal individuals, excluding a reduction in beta-receptor responsiveness as a cause of impaired sympathetic influence. Norepinephrine depletion, however, is a well-recognized concomitant of cardiac failure. It is possible that the reduction in sympathetically mediated heart rate responses results in part from depletion of the sympathetic neurotransmitter.
Subject(s)
Autonomic Nervous System/physiopathology , Heart Diseases/physiopathology , Heart Rate , Heart/innervation , Adolescent , Adult , Atropine , Cardiomyopathies/physiopathology , Exercise Test , Female , Heart Rate/drug effects , Heart Valve Diseases/physiopathology , Humans , Isoproterenol , Male , Middle Aged , Mitral Valve Stenosis/physiopathology , Nitroglycerin , Parasympathetic Nervous System/physiopathology , Sympathetic Nervous System/physiopathologySubject(s)
Heart Septal Defects, Atrial/physiopathology , Hemodynamics , Physical Exertion , Tetralogy of Fallot/physiopathology , Adolescent , Adult , Blood Pressure , Cardiac Catheterization , Cardiac Output , Female , Follow-Up Studies , Heart Rate , Heart Septal Defects, Atrial/surgery , Humans , Male , Middle Aged , Oxygen/blood , Oxygen Consumption , Posture , Pulmonary Artery , Pulmonary Veins , Rest , Tetralogy of Fallot/surgery , Vascular ResistanceSubject(s)
Myocardial Infarction/complications , Myocardial Infarction/etiology , Myocardial Infarction/physiopathology , Ventricular Fibrillation/therapy , Acute Disease , Animals , Arrhythmias, Cardiac/physiopathology , Atropine/administration & dosage , Atropine/therapeutic use , Coronary Vessels , Dogs , Injections, Intravenous , Lidocaine/administration & dosage , Lidocaine/therapeutic use , Ligation , Pacemaker, Artificial , Tachycardia/drug therapy , Tachycardia/etiology , Tachycardia/physiopathology , Tachycardia/therapy , Ventricular Fibrillation/drug therapy , Ventricular Fibrillation/etiology , Ventricular Fibrillation/physiopathologySubject(s)
Heart Ventricles/physiopathology , Hypertension, Pulmonary/physiopathology , Pericardium/physiology , Animals , Biomechanical Phenomena , Cardiac Catheterization , Cardiac Output , Cardiac Volume , Cats , Constriction , Heart Failure/etiology , Hypertension, Pulmonary/etiology , Norepinephrine/pharmacology , Papillary Muscles/drug effects , Papillary Muscles/physiopathology , Pulmonary Artery , Time FactorsSubject(s)
Funnel Chest/physiopathology , Heart/physiopathology , Adolescent , Adult , Cardiac Catheterization , Cardiac Output , Electrocardiography , Exercise Test , Female , Funnel Chest/diagnostic imaging , Funnel Chest/surgery , Hemodynamics , Humans , Lung/physiopathology , Male , Oxygen/blood , Oxygen Consumption , Phonocardiography , Physical Exertion , Posture , Pulmonary Artery , Radiography , Respiratory Function TestsSubject(s)
Adenylyl Cyclases/metabolism , Glucagon/pharmacology , Heart Failure/metabolism , Papillary Muscles/drug effects , Papillary Muscles/physiopathology , Adolescent , Adult , Binding Sites , Cardiac Catheterization , Female , Heart/drug effects , Heart Rate , Humans , In Vitro Techniques , Male , Middle Aged , Myocardium/analysis , Norepinephrine/pharmacology , Papillary Muscles/enzymologySubject(s)
Cardiac Volume , Heart Failure/physiopathology , Heart/physiopathology , Tricuspid Valve Insufficiency/physiopathology , Animals , Cardiac Catheterization , Cardiomegaly/etiology , Cardiomegaly/physiopathology , Constriction , Dogs , Electrocardiography , Heart Failure/etiology , Heart Ventricles/physiopathology , Myocardium/metabolism , Norepinephrine/metabolism , Pulmonary Artery/surgery , Stress, Physiological/etiology , Stress, Physiological/physiopathology , Tricuspid Valve Insufficiency/etiologySubject(s)
Angina Pectoris/etiology , Hemodynamics , Myocardium/metabolism , Nutritional Physiological Phenomena , Oxygen Consumption , Physical Exertion , Adult , Angina Pectoris/metabolism , Angina Pectoris/physiopathology , Blood Pressure , Eating , Female , Heart Rate , Humans , Male , Middle Aged , Time FactorsSubject(s)
Angina Pectoris/diagnosis , Physical Exertion , Adult , Angina Pectoris/physiopathology , Aorta , Blood Pressure , Brachial Artery , Carotid Sinus , Electric Stimulation , Electrocardiography , Heart/drug effects , Heart Rate , Hemodynamics , Humans , Male , Middle Aged , Myocardium/metabolism , Nitroglycerin/pharmacology , Oxygen Consumption , Pressoreceptors , Pulse , Time FactorsSubject(s)
Furans/pharmacology , Heart/drug effects , Hemodynamics/drug effects , Nitrates/pharmacology , Nitroglycerin/pharmacology , Adult , Aged , Angina Pectoris/drug therapy , Angina Pectoris/physiopathology , Blood Pressure/drug effects , Clinical Trials as Topic , Drug Synergism , Electrocardiography , Heart Rate/drug effects , Humans , Isosorbide Dinitrate/pharmacology , Isosorbide Dinitrate/therapeutic use , Middle Aged , Myocardium/metabolism , Nitroglycerin/therapeutic use , Oxygen Consumption/drug effects , Physical Exertion , Placebos , Time FactorsSubject(s)
Digitalis Glycosides/pharmacology , Heart/drug effects , Isoproterenol/pharmacology , Ouabain/pharmacology , Animals , Blood Flow Velocity , Blood Pressure/drug effects , Cardiac Output/drug effects , Dogs , Drug Synergism , Electric Stimulation , Heart Rate/drug effects , Time Factors , Ventricular Fibrillation/chemically inducedSubject(s)
Circadian Rhythm , Fibrinolysis , Physical Exertion , Adult , Arteries , Fasting , Female , Fibrin , Fibrinogen/analysis , Fibrinolytic Agents/analysis , Food , Humans , Male , Oxygen Consumption , Plasminogen/analysis , Rest , Time Factors , VeinsABSTRACT
The role of skin and muscle vascular beds in baroreceptor-mediated alterations of peripheral vascular resistance was evaluated in six normal subjects in whom the skin circulation in one forearm was temporarily suppressed by epinephrine iontophoresis. Baroreceptor activity was enhanced by application of negative pressure to the neck (neck suction) and inhibited by application of lower body negative pressure. Forearm blood flow was measured simultaneously in both arms with strain gauge plethysmographs. Since blood flow in the treated arm consisted entirely of muscle flow, skin flow was calculated from the difference between total forearm flow in the intact arm and muscle flow in the treated arm. Vascular resistances were calculated as the ratio of mean arterial pressure to the blood flow of each vascular bed. During neck suction, mean arterial pressure decreased from an average of 89 to 75 mm of Hg (P < 0.005), heart rate decreased from an average of 60 to 55 beats/min (P < 0.005), and total skin and muscle flows remained essentially unchanged. Cutaneous vascular resistance decreased from an average of 75 to 49 mm of Hg/ml per 100 g per min (P < 0.05), muscle vascular resistance from 68 to 51 (P < 0.005), and total forearm vascular resistance from 36 to 24 (P < 0.025). During lower body negative pressure, heart rate increased from an average of 59 to 69 beats/min (P < 0.005), mean arterial pressure did not change significantly, and significant decreases occurred in forearm blood flow from 5.4 to 2.7 ml/100 g per min, in skin blood flow from 3.1 to 1.4, and in muscle blood flow from 2.3 to 1.3. Cutaneous vascular resistance increased from an average of 47 to 110 mm of Hg/ml per 100 g per min (P < 0.05), muscle vascular resistance from 43 to 72 (P < 0.005), and total forearm vascular resistance from 20 to 38 (P < 0.001). These results demonstrate that both the skin and muscle resistance vessels participate in reflex changes initiated by alterations in baroreceptor activity.