Vagal techniques for termination of paroxysmal supraventricular tachycardia

Maneuvers that reflexly increase vagal tone were deployed to terminate the tachycardia in 68 consecutive patients with paroxysmal supraventricular tachycardia. The order and success rate of the protocol was as follows: 57 episodes were terminated with carotid sinus pressure alone or after pretreatment with edrophonium, 5 were terminated with the Valsalva maneuvers and 6 were terminated with phenylephrine. Potency testing showed that phenylephrine evoked the greatest increase in vagal tone. All cases demonstrated slowing of tachycardia ranging from 40 to 220 ms ± standard error of the mean (mean 79.0 ± 3.8 ms) followed by abrupt termination. Pauses after termination ranged from 900 to 3,300 ms (mean 1,683.8 ± 66.6) with 54 patients showing pauses of 2,000 ms or less. Termination was highly reproducible showing an overall success of 148 (92 percent) of 160 trials among 22 selected cases. The extent of increased vagal tone needed to terminate paroxysmal supraventricular tachycardia was raised by augmented sympathetic tone (infusion of isoproterenol) and decreased by reduced sympathetic tone (pretreatment with propranolol). Thus, paroxysmal supraventricular tachycardia can be rapidly, safely and consistently terminated by maneuvers that reflexly increase vagal tone.     

Detection of acute myocardial infarction by technetium-99m polyphosphate

Experimental work has shown that technetium-99m (^99mTc) pyrophosphate accumulates in recently infarcted myocardium and can be detected by external imaging techniques. Twenty-two ^99mTc polyphosphate myocardial studies were performed in 17 patients (in 3 after cardiac surgery) 3 to 20 days after myocardial infarction. Seventeen myocardial studies were performed in 17 control patients (in 6 after cardiac surgery). Twenty millicuries of ^99mTc polyphosphate was injected intravenously 60 to 120 minutes prior to gamma camera imaging in several views. Myocardial images were processed by the Gamma-11 computer system using standardized background subtraction and contrast enhancement. Results of 16 myocardial studies performed 4 to 20 days after transmural myocardial infarction in 12 patients were positive in 13 instances and questionable in 1. The location of the myocardial infarction by imaging corresponded to location by standard electrocardiographic criteria in 8 of the 10 patients with positive findings. In five patients with nontransmural myocardial infarction, results of myocardial imaging were positive in two, questionable in one and normal in one. In one patient with questionable findings results were normal when imaging was repeated 16 days after nontransmural myocardial infarction. Results of 17 control myocardial imaging studies were normal in 16 and questionable in 1. Therefore, ^99mTc polyphosphate myocardial imaging appears promising in the detection and location of transmural myocardial infarction. Its accuracy in detecting nontransmural myocardial infarction may be increased with greater experience and development of sophisticated digital analysis techniques. The method may prove useful in clinical situations such as cardiac surgery in which standard diagnostic aids are difficult to interpret.     

Reflex mechanisms responsible for early spontaneous termination of paroxysmal supraventricular tachycardia

The incidence and possible mechanism of early spontaneous termination of paroxysmal supraventricular tachycardia was studied in 20 consecutive patients. Episodes of induced tachycardia that terminated spontaneously within the 1st minute after initiation were included. Tachycardias ending spontaneously were associated with a reproducible course of hypotension at the onset followed by blood pressure recovery above control levels and termination. Spontaneous termination of tachycardias occurred within the A-V node 18 to 45 seconds (mean +/- standard error of the mean 27.9 +/- 5.3) after their onset. In the supine position (0 degrees) 9 (45 percent) of 20 patients showed spontaneous termination in 36 (16 percent) of 219 episodes of tachycardia. In the head-dependent position (-20 degrees) only 1 (8 percent) of 13 patients manifested spontaneous termination in 2 (4 percent) of 54 episodes. In the head up position (+60 degrees) only 1 (6 percent) of 18 patients exhibited termination in 2 (2 percent) of 102 episodes. After partial cholinergic blockade with intravenous hyoscine butylbromide, 20 mg, or atropine, 0.6 mg, none of five patients showed spontaneous termination in 25 episodes. After beta adrenergic blockade with 10 mg of propranolol intravenously, none of 16 patients showed spontaneous termination in 87 episodes of tachycardia. We conclude that the initial hypotension during tachycardia evokes a sympathetic response that increases blood pressure and this increase in turn causes a rise in vagal tone that breaks the tachycardia.     

Effect of intravenous and intracoronary nitroglycerin on left ventricular wall motion and perfusion in patients with coronary artery disease

Left ventricular anterior wall motion and distribution of coronary perfusion were assessed by contrast cineangiography and the dual isotope-labeled intracoronary microsphere technique before and after intravenous or intracoronary administration of nitroglycerin in 30 patients with significant left anterior descending coronary artery disease and resting anterior wall asynergy. Perfusion was measured in 11 additional control patients before and after administration of saline solution. Reversible asynergy was observed in 6 (43 percent) of 14 patients after systemic (intravenous) nitroglycerin and in 7 (44 percent) of 16 patients after intracoronary nitroglycerin. Significant reductions of blood pressure and improved wall motion were noted in both groups receiving nitroglycerin, suggesting afterload reduction as the common mechanism. There was also a small increase in end-diastolic volume index in patients with reversible asynergy after intracoronary administration of nitroglycerin, but no significant trends in preload change after intravenous administration. Ejection fraction increased significantly in patients with reversible asynergy after both intravenous and intracoronary nitroglycerin. Both intravenous and intracoronary nitroglycerin resulted in significant increases and decreases in distribution of coronary perfusion to the anterior wall. However, these changes were randomly distributed and improved perfusion did not consistently occur with improved wall motion.In conclusion, both intravenous and intracoronary nitroglycerin may reverse wall motion asynergy and produce both favorable and unfavorable changes in perfusion in patients with coronary disease. The common mechanism in improving wall motion with either intravenous or intracoronary nitroglycerin was afterload reduction, suggesting that the systemic effects of nitroglycerin are the most important in reversing asynergy.     

Cannon waves with A-V association.

Under appropriate circumstances, cannon waves can occur in the presence of A-V associated rhythms. Presented here is a case of first degree A-V block with cannon waves. Recognition of these waves and their behavior aided in diagnosing the patient's rhythm. The cannon waves were documented by jugular venous pulse recordings.     

Carotid sinus massage induced elimination of rate related bundle branch block during paroxysmal atrial tachycardia: A simple method of proving bypass tract participation in the tachycardia

Four cases of paroxysmal atrial tachycardia are described in whom rate related left bundle branch block (LBBB) was often present which persisted indefintely and showed no signs of spontaneous disappearance. Transient slowing of the tachycardia by carotid sinus massage in each case eliminated LBBB and this led to tachycardia acceleration. The tachycardia acceleration was traceable to a shortening in ventriculoatrial conduction. These observations proved the participation of a left sided bypass tract in the tachycardia circuit in each of these cases.     

Rest and exercise ventricular function in adults with congenital ventricular septal defects

Rest and exercise right and left ventricular function were compared using equilibrium gated radionuclide angiography in 19 normal sedentary control subjects (mean age 28 years, range 22 to 34) and 34 patients with hemodynamically documented congenital ventricular septal defect (VSD) (mean age 27 years, range 20 to 40). The 34 patients with VSD were divided into 3 groups: those in Group 1 (17 patients) had pulmonary to systemic blood flow ratios of less than 2 to 1; those in Group 2 (12 patients) had prior surgical closure of VSD (mean interval from surgery 17 years, range 9 to 22), and those in Group 3 (5 patients) had Eisenmenger's complex. Gated radionuclide angiography was performed at rest and during each level of graded supine bicycle exercise to fatigue. Heart rate, blood pressure, maximal work load achieved, and right and left ventricular ejection fractions were assessed. The control subjects demonstrated an increase in both the left and right ventricular ejection fractions with exercise (0.70 +/- 0.07 to 0.79 +/- 0.05 and 0.46 +/- 0.06 to 0.57 +/- 0.04; p less than 0.001 for left and right ventricles, respectively). All study groups failed to demonstrate an increase in ejection fraction in either ventricle with exercise. Furthermore, resting left ventricular ejection fraction in Groups 2 and 3 was lower than that in the control subjects (0.59 +/- 0.09 and 0.54 +/- 0.06 versus 0.70 +/- 0.07; p less than 0.001) and resting right ventricular ejection fraction was lower in Group 3 versus control subjects (0.30 +/- 0.07 versus 0.46 +/- 0.06; p less than 0.001). Thus (1) left and right ventricular function on exercise were abnormal in patients with residual VSD as compared with control subjects; (2) rest and exercise left ventricular ejection fractions remained abnormal despite surgical closure of VSD in the remote past; (3) resting left and right ventricular function was abnormal in patients with Eisenmenger's complex; (4) lifelong volume overload may be detrimental to myocardial function.     

Severe alcoholic cardiomyopathy reversed with abstention from alcohol

In a chronic alcoholic with a severe congestive cardiomyopathy the angiographic and hemodynamic evidence of left ventricular dysfunction was completely reversed after 1 year of abstinence. At the time of initial presentation two of the traditional hallmarks of a poor prognosis were present, namely, a long exposure to alcohol before the onset of symptoms and severe diffuse left ventricular dilatation and hypokinesis (ejection fraction 14.9 percent). Yet, today, 18 months later he is asymptomatic, receiving no medications and has normal left ventricular function. A reexamination of prognostic factors in alcoholic cardiomyopathy may be indicated.     

Improved diagnosis in coronary cinearteriography with routine use of 110 degrees oblique views and cranial and caudal angulations. Comparison with standard transverse oblique views in 100 patients.

Conventionally mounted X-ray systems for coronary cinearteriography limit angulation of the X-ray beam to the transverse plane of the patient, and use of the motorized cradle restricts rotation to 60 degrees to 70 degrees. These limitations of available projections seriously hamper adequate examination of the coronary arteries. With use of the Siemen's Cardoskop-U, which was designed to overcome this problem, the coronary arteries of 100 consecutive patients were examined with standard oblique projections, and in addition with cranial and caudal angulated oblique and 110 degrees oblique projections. These arteriograms were independently examined by two expert observers. In approximately 20 percent of patients the additional views unmasked lesions that would otherwise have been missed. In a further 34 percent the diagnosis was significantly improved because the full extent of a lesion was revealed, overlap of branches was avoided or the degree of an eccentric stenosis was upgraded. In 4 of 12 patients with apparently normal arteriograms in standard projections, lesions were unmasked by the additional views.     

Demand pacemaker slowing: a simple bedside technique

We present a simple noninvasive bedside technique to slow gradually any R-wave inhibited ventricular demand pacemaker up to one-half its original rate for indefinite periods of time. Gradual pacemaker slowing allows accurate diagnostic observations and therapeutic interventions in pacemaker-induced arrhythmias and may possibly be used in the management of unstable angina in patients with ventricular demand pacemakers.     

Long-term angiographic assessment of the influence of coronary risk factors on native coronary circulation and saphenous vein aortocoronary grafts.

The influence of smoking, hyperlipidemia, and glucose intolerance on graft patency and rate of progression of obstructive disease in the native circulation was assessed in 99 patients 1 1/2 years after aortocoronary bypass grafting. There were 24 patients in whom none of these risk factors was identified. There were 42 patients with one, 29 with two, and four with three risk factors. Overall graft patency rate was 74%. Graft patency was not significantly influenced by any of these factors either singly or in combination. Progression of obstructive disease in both proximal and distal segments of grafted vessels and in nongrafted vessels was not significantly increased by the presence of one, two, or three risk factors. Over all, there was progression in 56% of segments proximal to grafts, in 8% distal to grafts, and in 14% of nongrafted vessels. Longer term studies will be required to establish any adverse influence of these risk factors on saphenous vein bypass grafts and native circulation.     

The metabolic response to the euglycemic insulin clamp in type I diabetes and normal humans

The euglycemic insulin clamp has been utilized extensively to measure in vivo tissue sensitivity to insulin under various circumstances. Insulin sensitivity is determined from the amount of glucose metabolized under steady state conditions. To assess the effect of abnormalities in other insulin responsive metabolic pathways on glucose metabolism and thus insulin sensitivity as measured by the glucose clamp, the concentration of lactate, pyruvate, 3-hydroxybutyrate, glycerol, alanine, and free fatty acids were measured at baseline and during a two-hour euglycemic clamp in 13 nonobese subjects with type I diabetes. The observed responses were compared to 11 normal controls. Insulin sensitivity as measured by M (glucose metabolized), MCRg (metabolic clearance of glucose), and M/I ratio (glucose metabolized per unit insulin) were all significantly decreased in the diabetic subjects (P less than 0.005). Free fatty acids (FFA) and 3-hydroxybutyrate were significantly elevated at baseline in the diabetic subjects (P less than 0.05) and decreased significantly at 60 and 120 minutes in both groups. Baseline blood pyruvate and lactate concentrations were similar in the control and diabetic subjects. Pyruvate increased significantly at 60 minutes in both groups (P less than 0.05) and returned to baseline in the control subjects but remained elevated at 120 minutes in the diabetic subjects (P less than 0.001). Lactate increased similarly in both groups and remained elevated at 60 and 120 minutes. In summary, insulin sensitivity as assessed by the euglycemic insulin clamp is decreased in type I diabetes. However, specific differences in the concentration of several other metabolites both at baseline and in response to hyperinsulinemia were also identified in the diabetic subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

The metabolic response to glycemic control by the artificial pancreas in diabetic man.

To determine the effect of glycemic control by the artificial pancreas on the other metabolic consequences of diabetes, five renebese male insulin-dependent diabetic subjects were studied first on s.c. insulin and then during artificial pancreas (AEP) control. Glycemia was continuously monitored, and the circulating concentrations of factate, pyruvate, alanine, free fatty acids (FFA), beta hydroxybutyrate, and triglycerides were measured during breakfast, lunch, snack, and supper. The metabolic profiles were compared to normal control subjects. Glycemic excursion with meals during AEP control was normalized (min, 76 ± 8 mg/dl; max, 157 ± 20 mg/dl), compared to administration of s.c. insulin (min, 173 ± 52; max, 279 ± 49 mg/dl). Postabsorptive concentrations of lactate and pyruvate were elevated for diabetic subjects on s.c. insulin treatment and during AEP control. However, the postmeal peaks of lactate and pyruvate observed in the normal control individuals were restored during AEP control. Although alanine concentrations were similar for all groups at the start of the experiment, the postprandial increase that occurred with breakfast for the normal subjects was delayed until lunch for both diabetic groups. The elevated FFA concentrations with s.c. insulin were entirely normalized during AEP control, whereas beta hydroxybutyrate concentrations were incompletely corrected. These studies demonstrate that a short period of glycemic control during meals restores toward normal other metabolic intermediates influeneed by insulin. For further refinement in metabolic control, a more prolonged period of normoglycemia may be required.     

Detection of entrapped intracardiac air with intraoperative echocardiography

Embolization of entrapped intracardiac air represents a significant risk to the patient undergoing open heart surgery. To date, there have been no means available to ensure that the heart is free of air prior to restoration of the circulation. To assess Whether M mode echocardiography can accurately detect intracardiac air, we studied 10 dogs during cardiopulmonary bypass. Randomly, air was or was not injected into the left ventricular cavity of the fibrillating heart. Intracardiac air could be recognized by the presence of a stippled granular pattern, or a loss of the discrete linear echoes or decreased far field echoes, or any combination of these three. In all, 131 random observations were made. When 1.0 cc of air was injected, sensitivity and specificity were both 100 percent, but when 0.2 cc was injected, sensitivity and specificity decreased to 86 and 58 percent, respectively. Thus, M mode echocardiography appears to provide a sensitive and specific tool for detecting intracardiac air.