bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of the site of ventricular preexcitation with body surface maps in patients with Wolff-Parkinson-White syndrome.
Authors: Benson D W , Sterba R , Gallagher J J , Walston A , Spach M S
Published: June 2011

Forty-nine patients with Wolff-Parkinson-White syndrome, ages 7 weeks to 51 years, were studied with isopotential body surface maps during normal sinus rhythm, atrial pacing or induced atrial fibrillation. The location of the accessory pathway was determined by multicather electrophysiologic study or surgical ablation of the accessory pathway. When fusion was minimized and ventricular activation primarily controlled by a single accessory pathway, the distribution of positive and negative potentials on the anterior and posterior torso during QRS (observed at 40 msec) and the ST segment were an excellent index of the location of the site of the accessory pathway. The relationship between a specific sequence of QRS-T wave body surface maps and a specific preexcitation site was similar from patient to patient in the presence of marked differences in age, size, and different cardiac status due to structural congenital cardiac defects. The localization of the site of the accessory pathway using distributions too early in QRS (before 40 msec) was unreliable because the early distributions varied from patient to patient for the same preexcitation site; however, the potential distributions during the ST segment were both stable and consistent from patient to patient for the same preexcitation site. The presence of significant fusion of ventricular activation initiated via a single accessory pathway and the normal conduction system or via multiple accessory pathways complicated the interpretation of body surface distributions. Thus, one can predict accurately at least seven preexcitation sites by the combined use of QRS and ST-segment body surface maps.
Employment status after coronary artery bypass surgery.
Authors: Smith H C , Hammes L N , Gupta S , Vlietstra R E , Elveback L
Published: June 2011

Factors that influence the effect of coronary artery bypass graft surgery (CABG) on employment were examined in 1427 2-year survivors from entry into the nonrandomized Mayo Clinic portion of the National Heart, Lung, and Blood Institute's prospective Coronary Artery Surgery Study. Five hundred seventy-nine patients (41%) were treated medically, 769 (54%) were treated surgically and 79 (5%) were initially treated medically but later had CABG. All groups were similar at entry with respect to age and percent working, retired or quitting work for cardiac reasons. There was a similar decline in employment from entry to 2 years in all three groups. The number who quit work for cardiac reasons was twice the number of previously disabled workers who returned to work with all three modes of therapy. Univariate and multivariate analyses were used to test the independent prognostic values of a number of variables for subsequent employment in the largest homogeneous surgical subset--496 nonretired males. Postoperative angina was the most powerful factor reducing postoperative employment. Postoperative employment was also lower if the patient was not working before surgery, was a laborer, or older than age 55 years (all p less than 0.01). Although the level of nonwork physical activity was generally increased after CABG, there was no relationship between physical activity and employment. This study confirms that employment declines after CABG, but three of the four most powerful prognostic variables were not related to surgery.
Management of the patient with coronary artery disease. A surgeon's perspective.
Authors: Willman V L
Published: June 2011

The patient who has symptomatic coronary artery disease suffers from a chronic, incurable illness. The physician must help such a patient adapt to the disease. Coronary artery bypass surgery is, in many instances, a valuable therapeutic adjunct that provides both physiologic and psychologic benefit. It frees many patients from angina pectoris and, in some instances, prolongs life. It often gives the patient the confidence of knowing that maximum effort is being expended to combat the disease. Selectively used, coronary artery bypass is an effective component in the total management of patients with coronary artery disease.
Effects of digitalis on subendocardial and subepicardial dysfunction during acute ischemia.
Authors: Banka V S , Yamazaki H , Agarwal J B , Bodenheimer M M , Helfant R H
Published: June 2011

The effects of digitalis (ouabain infusion, priming dose of 10 micrograms/kg/min followed by 2.0 micrograms/kg/min) on subepicardial and subendocardial ischemic dysfunction during partial occlusion (59.4% reduction in coronary flow) and total coronary occlusion were evaluated in 14 dogs using pairs of ultrasonic crystals implanted in the epicardial and endocardial layers. After 30 minutes of partial coronary occlusion, systolic shortening in the ischemic zone decreased from 12.4 +/- 2.9% to -0.4 +/- 0.9% (p less than 0.001) in the epicardium and from 18.9 +/- 3.1% to -1.0 +/- 1.1% (p less than 0.001) in the endocardium. Ouabain infusion increased the systolic shortening from -0.4 +/- 0.9% to 10.6 +/- 3.1% (p less than 0.001) in the epicardium and from -1.0 +/- 1.1% to 17.2 +/- 3.4% (p less than 0.001) in the endocardium. The end-diastolic length did not change. In contrast, after 30 minutes of total coronary occlusion, systolic shortening in both epicardial and endocardial layers was replaced by systolic lengthening and remained unaffected by ouabain infusion in both layers. Systolic shortening in the nonischemic epicardial and endocardial layers increased consistently. We conclude that ouabain improves the contractile function of both ischemic epicardial and endocardial layers layers after partial coronary occlusion and does not worsen subendocardial ischemic dysfunction. After total coronary occlusion, however, the contraction of the ischemic zone is unaffected by ouabain.
Effects of verapamil and propranolol on left ventricular systolic function and diastolic filling in patients with coronary artery disease: radionuclide angiographic studies at rest and during exercise.
Authors: Bonow R O , Leon M B , Rosing D R , Kent K M , Lipson L C , Bacharach S L , Green M V , Epstein S E
Published: June 2011

To determine the effects of verapamil on left ventricular (LV) systolic function and diastolic filling in patients with coronary artery disease (CAD), we performed gated radionuclide angiography at rest and during exercise in 16 symptomatic patients before and during oral verapamil therapy (480 mg/day). Twelve patients were also studied during oral propranolol (160--320 mg/day). LV ejection fraction at rest was normal in 13 patients, but abnormal diastolic filling at rest, defined as peak filling rate (PFR) less than 2.5 end-diastolic volumes (EDV)/sec or time to PFR greater than 180 msec, was present in 15. During verapamil, resting ejection fraction decreased (control 50 +/- 10% [+/- SD), verapamil 45 +/- 12%, p less than 0.005), but resting diastolic filling improved: PFR increased (control 1.9 +/- 0.6 EDV/sec, verapamil 2.3 +/- 0.9 ECV/sec, p less than 0.005) and time to PFR decreased (control 185 +/- 38 msec, verapamil 161 +/- 27 msec, p less than 0.05). Exercise ejection fraction did not change during verapamil (control 42 +/- 13%, verapamil 43 +/- 12%, NS), but exercise PFR increased (control 3.1 +/- 0.9 EDV/sec, verapamil 3.6 +/- 1.1 EDV/sec, p less than 0.05) and exercise time to PFR decreased (control 108 +/- 30 msec, verapamil 91 +/- 17 msec, p less than 0.05). In contrast, propranolol did not alter ejection fraction, PFR, or time to PFR at rest or during exercise. Thus, LV ejection fraction is decreased by verapamil at rest but is unchanged during exercise. While LV systolic function is not improved by verapamil, LV diastolic filling is enhanced by verapamil, both at rest and during exercise. These mechanisms may account in part for the symptomatic improvement in many patients during verapamil therapy.
Propranolol in angina pectoris. Comparison of long-acting and standard-formulation propranolol.
Authors: Parker J O , Porter A , Parker J D
Published: June 2011

In a double-blind, crossover study in 20 patients with stable angina pectoris, the effects of long-acting propranolol, 160 mg administered once daily for 4 weeks, were compared with those of standard propranolol, 40 mg given four times daily for 4 weeks. The patients suffered no adverse effects when they were switched between treatment schedules. The average number of episodes of angina during the 4 weeks on long-acting propranolol was 7.3 and on standard propranolol. 6.3. Average nitroglycerin consumption was 5.8 and 4.9 tablets during therapy with these two drug programs. The resting values for heart rate, systolic blood pressure and rate-pressure product were similar when determined 25.4 hours after a dose of long-acting propranolol and 10.7 hours after standard propranolol. When the patients exercised at these times, patients on long-acting propranolol and standard propranolol had similar walking times to the onset of angina and to the development of moderate angina. The values for heart rate, systolic blood pressure and rate-pressure product were similar at rest and during exercise during these two treatment programs. We conclude that long-acting propranolol administered in a dose of 160 mg daily is as effective as 50 mg of standard propranolol four times daily.
The relationship between the strength of the human heart beat and the interval between beats.
Authors: Pidgeon J , Miller G A , Noble M I , Papadoyannis D , Seed W A
Published: June 2011

In 15 patients undergoing cardiac catheterization and pacing tests, the left ventricular (LV) pressure and its maximum rate of rise (LV dP/dt max) were measured with catheter-tip manometers. Atrial or ventricular pacing at a single steady frequency (the priming frequency) was followed by a test pulse at a varying interval (test pulse interval). In 14 subjects in whom it was examined, the contractile response after the test pulse increased with test pulse interval to reach a maximum plateau value--the optimum contractile response (OCR). In five cases, further prolongation of the test pulse interval decreased the contractile response. The optimum test pulse interval occurred at 800-900 msec. An increase in the priming frequency before the introduction of the test pulse caused a progressive increase in OCR, in contrast to the minor effects on LV dP/dt max of the control beats. Similar results were recorded in four other patients in whom contractile response was assessed from the rate of rise of right ventricular pressure. These results indicate that with tachycardia, the interval between beats is insufficient to allow maximum contractile performance (presumed to be activated by calcium ions) to develop. The true effect of increasing heart rate is only revealed by the relationship between OCR and the preceding frequency of contraction.
Mechanisms of bradycardia-induced ventricular arrhythmias in myocardial ischemia and infarction.
Authors: Scherlag B J , Kabell G , Harrison L , Lazzara R
Published: June 2011

Experimental and clinical cases have been described in which bradycardia, i.e., heart rates below 60 beats/min or slowing of the heart rate, resulted in lethal ventricular arrhythmias during various stages of myocardial ischemia and infarction. The present study was designed to determine the relationship of lethal ventricular arrhythmias and slow heart rates. In 18 dogs anesthetized with sodium pentobarbital, the left anterior descending (LAD) coronary artery was ligated. Standard ECGs, His bundle electrograms and composite electrograms from intramural and epicardial areas in ischemic and normal zones were recorded during the first 3 hours of ischemia. Vagosympathetic trunk stimulation caused varying degrees of slowing and bradycardia. Of the 18 dogs, slowing of the heart rate or marked bradycardia induced ventricular ectopic beats coupled to the sinus beats in two, sustained ventricular tachycardia in two, and ventricular fibrillation in two. In another group of six dogs studied 17-25 days after LAD ligation, one dog showed sustained ventricular tachycardia in response to vagal-induced bradycardia. In all acute or chronic cases of arrhythmias after LAD ligation, continuous electrical activity was recorded on one or more of the electrograms within or overlying the ischemic or infarcted zones. This bridging electrical activation, which is indicative of slow conduction, provided strong presumptive evidence for reentry as the mechanism of lethal or potentially lethal ventricular arrhythmias triggered by bradycardia in the setting of myocardial infarction.
Rapid renal clearance of immunoreactive canine plasma myoglobin.
Authors: Klocke F J , Copley D P , Krawczyk J A , Reichlin M
Published: June 2011

Rates and mechanisms of myoglobin removal from plasma were examined in closed-chest dogs, using disappearance patterns of immunoreactivity and radioactivity after i.v. canine myoglobin radiolabeled with 125I. Arterial immunoreactive myoglobin concentration decreased monoexponentially over a 2-decade range, with rate constants of disappearance averaging -0.080 +/- 0.014 min-1 (+/- SD) (corresponding to half-times of disappearance of 8.9 +/- 1.5 min). Renal arteriovenous difference in immunoreactive myoglobin concentration documented extraction of the parent molecule, with extraction ratios averaging 0.36 +/- 0.06. Renal venous specific activity increased a few minutes after myoglobin administration, consistent with discharge from the kidney of nonimmunoreactive radiolabeled peptides of the parent molecule. Arterial disappearance of 125I was subsequently delayed in relation to immunoreactive myoglobin. Urinary recoveries of immunoreactive parent molecule and radiolabeled constituents were limited, averaging 2.5 +/- 1.1% and 12 +/- 1.1% over a 6-hour period. Arterial rate, constants of disappearance of immunoreactive myoglobin decreased markedly with decreases in renal perfusion produced by obstruction of renal arterial inflow. We conclude that myoglobin entering the vascular space is normally cleared rapidly by renal catabolism. Seven myoglobin concentration-time patterns during acute myocardial infarction directly reflect patterns of protein entry into the vascular space after release from injured tissue.
The reasonable workup before recommending medical or surgical therapy: an overall strategy.
Authors: Friesinger G C
Published: June 2011

The workup of a patient with chronic ischemic heart disease (IHD) before the selection of medical-surgical or medical therapy depends on multiple objective and subjective factors. These include symptoms, extent of anatomic disease (degree of coronary arteriosclerosis and left ventricular abnormalities), objective evidence of ischemia, extent of left ventricular dysfunction, and recent intercurrent ischemic events. In a minority of patients, a single factor is of overwhelming importance; e.g., the presence of severe left main coronary artery narrowing in a symptomatic patient indicates surgery is a better choice, whereas evidence of advanced left ventricular dysfunction suggests that surgery is likely to be risky and of limited help to the patient. In most instances, multiple factors should be considered before making a recommendation. The patient should be placed in the appropriate clinical subset and the objective factors that are most important in determining survival should be evaluated. Hence, an exercise electrocardiographic study to evaluate symptoms and exercise tolerance in a patient with angina pectoris and radioventriculographic studies with exercise to estimate left ventricular performance in a patient who complains of fatigue and breathlessness are superior to the subjective interpretations of routine clinical examinations. Asymptomatic patients and those with excellent exercise tolerance pose the most difficult decisions. Perhaps serial (even annual) noninvasive evaluation is appropriate in such patients in light of the current uncertainty about how to manage them. Laboratory tests should be used selectively, systematically and sequentially. The high cost of many of the examinations is reason to avoid duplication. When noninvasive evaluation can answer the question being posed and the cost of hospitalization avoided, this should be done. However, there is little reason to perform noninvasive examinations that do not answer the clinical question being asked; hence, in many patients it is appropriate to proceed directly to coronary arteriography rather than to perform a variety of "screening" examinations before this procedure.
Aortocoronary bypass grafting: an internist's perspective.
Authors: McIntosh H D
Published: June 2011

Seven hundred fifty thousand to 1 million persons in this country have undergone aortocoronary bypass grafting since 1968, but many questions regarding the indications for the procedure and its advantages and disadvantages persist. Based on this surgical experience and on observations made during the last decade regarding nonoperative therapy and changes in the natural history of coronary heart disease, at least eight considerations should influence attitudes regarding the role of surgery: (1) The operation is a significant addition to the management of some patients with coronary heart disease. (2) The operative mortality in many centers is gratifyingly low. (3) Mortality from coronary heart disease in this country has declined strikingly during the past decade. (4) Because of the declining mortality from coronary heart disease, the prognosis of patients with the disease seen in 1980 is uncertain. (5) Coronary heart disease is a progressive disease and surgery does not prevent the progression of the disease in the native circulation. (6) Reports of therapeutic results, whether surgical or medical, are often biased toward the positive side. (7) Aortocoronary bypass does appear to postpone premature death in symptomatic patients with stenosis of the left main coronary artery, and possibly in symptomatic patients with three-vessel disease and modest impairment of left ventricular contractility. (8) Conclusions of meetings of "experts" regarding therapy may not by applicable to the country at large. The profession and the general public should be so informed.
Institutional variation of coronary artery bypass graft surgery: emphasis on myocardial protection.
Authors: Kaiser G C
Published: June 2011

There are institutional variations in the operative mortality of coronary artery bypass graft surgery (CABG). Patient selection, based on clinical and angiographic criteria, is a significant factor. Even after adjustment for patient selection, institutional differences remain. Operative experience and volume of cases are also related to institutional variations. Recent attention to the technique of myocardial preservation has highlighted its significance in reducing the incidence of perioperative myocardial infarction and operative mortality. Institutional heterogeneity also exists in the nonoperative management of ischemic heart disease. However, undetected factors probably significantly affect the outcome. These institutional variations emphasize a major advantage of randomized clinical trials--that they should equalize these unknown factors.
Left ventricular performance before and after aortocoronary artery bypass surgery.
Authors: Chesebro J H , Ritman E L , Frye R L , Smith H C , Vlietstra R E , Pluth J R
Published: June 2011

Left ventricular performance was studied before and late (mean 12-17 months) after aortocoronary artery bypass surgery by quantitative, computer-based videoangiography. We measured total function (left ventricular ejection fraction, volumes and end-diastolic pressure) at rest (in 60 patients) and before and after exercise (abnormal exercise hemodynamics preoperatively in 32 patients) and regional function (peak rate of systolic wall thickening) at rest (in 60 patients) and before and after administration of nitroglycerin (in 19 patients). Total left ventricular function at rest is usually unchanged postoperatively. Exercise hemodynamics are more sensitive indexes of performance and, if abnormal, usually improve postoperatively if revascularization has been complete and extensive myocardial infarction has not occurred. Regional myocardial function usually improves postoperatively if the bypass graft to the region is patent and has a blood flow of more than 60 ml/min (measured late postoperatively by videodensitometry) and if no previous infarction was present in the region. Myocardial infarction and graft blood flow of 40 ml/min or less are the two main factors that prevent improvement in abnormal regions defined by the regional wall thickening method when bypass grafts are patent. Regions supplied by occluded grafts show decreases in regional function. The preoperative wall-thickening response to administration of nitroglycerin can be used to distinguish ischemia and significant myocardial infarction and to predict the successful response to aortocoronary bypass graft surgery.
Serial evaluation of myocardial thickening and thinning in acute experimental infarction: identification and quantification using two-dimensional echocardiography.
Authors: Nieminen M , Parisi A F , O'Boyle J E , Folland E D , Khuri S , Kloner R A
Published: June 2011

Regional left ventricular function was studied serially by quantitative two-dimensional echocardiography (2-D echo) in 20 dogs after left anterior descending coronary artery ligation. Normal values for regional myocardial thickening were established in 20 healthy dogs and used as a standard to recognize abnormally contracting segments (ACS). In normal hearts, the mean percent thickening tended to increase from base (25.8%) to apex (34.0%), but showed considerable diversity from segment to segment (range 20.0-40.0%); nevertheless, at least some degree of thickening was seen in every segment. After coronary occlusion, myocardial segments either thinned or failed to thicken. At the papillary muscle level, there was an improvement in function between 2 and 48 hours, with thinning at 2 hours and thickening at 48 hours. Tissue infarct size (IS) determined at 48 hours was related to IS derived from a weighted summation of ACS at 2, 24 and 48 hours. At 2 hours, ACS considerably overpredicted and correlated poorly with tissue IS (25.3% vs 13.4%; r = 0.60); by 48 hours, IS predicted by ACS had decreased to 15.3% (p less than 0.05) and had an improved, but only fair correlation with tissue IS (r = 0.73, SEE = 4.9%). We conclude that there is considerable heterogeneity to myocardial thickening by 2-D-echo, but failure to thicken is not seen in the normal dog heart. In many dogs, the extent of myocardial dysfunction 2 hours after coronary ligation exceeds that seen later. Tissue IS is difficult to predict accurately from ACS. Since the amount of muscle dysfunction is not necessarily equivalent to the amount of tissue necrosis in acute myocardial infarction, ACS may be more appropriate used to tract the course of infarction rather than to predict IS.
Sudden death recorded during Holter monitoring.
Authors: Nikolic G , Bishop R L , Singh J B
Published: June 2011

Six instances of sudden death were recorded by Holter monitoring, which showed ventricular fibrillation in five and a bradyarrhythmia in one. Complex ventricular ectopic activity preceded cardiac arrest in five patients, including the one with the bradyarrhythmic arrest. Two patients with chronic bifascicular block arrested as a result of ventricular fibrillation. Fifteen cases reports from the literature are reviewed. The composite profile includes advanced myocardial disease (present in all cases), complex ventricular ectopic activity, R-on-T initiation of the terminal rhythm except in patients with prolonged QT interval, and variations in cycle length preceeding the onset of ventricular tachycardia or fibrillation. The role of supraventricular mechanisms in sudden death is uncertain.
Feasibility of altering type A behavior pattern after myocardial infarction. Recurrent Coronary Prevention Project Study: methods, baseline results and preliminary findings.
Authors: Friedman M , Thoresen C E , Gill J J , Ulmer D , Thompson L , Powell L , Price V , Elek S R , Rabin D D , Breall W S , Piaget G , Dixon T , Bourg E , Levy R A , Tasto D L
Published: June 2011

We studied 1035 consecutive postinfarction patients to determine the feasibility of altering type A behavior and the effect such alteration might have on subsequent rates of infarction and cardiovascular death. Approximately 300 subjects were enrolled in small groups and primarily received cardiologic counseling on the usually accepted coronary risk factors. Six hundred subjects received, in addition to cardiologic counseling, advice and instructions designed to diminish the intensity of their type A behavior. The remaining subjects, serving as controls, received no counseling, but were examined and interviewed annually, as were those who dropped out of counseling groups. More than 98% of the 1035 subjects exhibited moderate-to-severe type A behavior during a videotaped structured interview. After the first year of this 5-year study, the rates of infarction and cardiovascular death were lower (p less than 0.01 and p less than 0.05, respectively) among subjects who received both cardiologic and behavioral counseling than among the control subjects. The rate of nonfatal infarction was lower (p less than 0.05) among subjects who received behavioral counseling than among those who received only cardiologic counseling or those who dropped out of either counseling group. The circumstances that most often preceded recurrent infarction or cardiovascular death were emotional crisis, excess physical activity, ingestion of a single fatty meal or a combination of these phenomena.
Pulmonary atresia and intact ventricular septum: a revised classification.
Authors: Bull C , de Leval M R , Mercanti C , Macartney F J , Anderson R H
Published: June 2011

The dismal outlook for patients with pulmonary atresia with intact ventricular septum may be related to associated right ventricular hypoplasia. Study of 32 autopsy specimens and 46 angiocardiograms of neonates with this lesion suggested that the cavitary hypoplasia was related to massive hypertrophy of the right ventricular wall. This hypertrophy was sufficient to obliterate the trabecular and/or infundibular portion of the ventricular cavity entirely in one-third of the cases; this observation forms the basis for a revised classification of these hearts. Three autopsies and 14 angiograms of neonates with critical pulmonary stenosis were examined. Hearts with obliterated infundibular and trabecular cavities had thicker walls and smaller tricuspid valves, as estimated angiographically or at autopsy, than those in which the normal three portions of the ventricular cavity were represented.
Analysis of coronary responses to various doses of intracoronary nitroglycerin.
Authors: Feldman R L , Marx J D , Pepine C J , Conti C R
Published: June 2011

We studied the degree of coronary artery dilation resulting from increasing doses of intracoronary nitroglycerin (NTG). Heart rate, aortic pressure and coronary artery angiograms were recorded before and after 5-, 50-, 150- and 250-microgram doses of NTG infused into the left main coronary artery. Coronary artery diameters were measured by a magnification angiographic technique. After intracoronary NTG, heart rate was unchanged 2 minutes after each dose. Mean aortic pressure was unchanged after 5 microgram (NS), but declined 5 mm Hg (mean) after 50 microgram, 9 mm Hg after 150 microgram and 18 mm Hg after 250 microgram (all p less than 0.05) compared with before NTG. The maximal increase in diameter occurred after 150 microgram, and no additional increase was seen after 250 microgram. After 5- and 50-microgram doses, 67% and 75% maximal dilation responses, respectively, were observed. Compared with coronary artery diameter before NTG, the 150-microgram dose increased the diameter of left main coronary artery by 5%, proximal coronary artery segments by 9%, middle segments by 19%, distal segments by 34%, collateral-filled coronary arteries by 38%, coronary artery stenoses by 5%, and small coronary arteries (0.4-1.0 mm) by 54%. These data indicate that relatively small doses of intracoronary NTG produce potentially important coronary artery dilation without important changes in heart rate and aortic pressure. These observations should prove helpful in choosing dosage schedules for intracoronary NTG.
Prostacyclin-induced acute pulmonary vasodilation in primary pulmonary hypertension.
Authors: Rubin L J , Groves B M , Reeves J T , Frosolono M , Handel F , Cato A E
Published: June 2011

To evaluate the effects of prostacyclin (prostaglandin I2) on pulmonary vascular tone in primary pulmonary hypertension (PPH), we performed right-heart catheterization on seven patients with PPH and made hemodynamic measurements before and after infusing incremental doses of prostacyclin. In maximal doses of 2-12 mg/kg/min (mean 5.7 +/0 3.1 ng/kg/min), prostacyclin reduced mean pulmonary arterial pressure from 62 +/- 15 to 55 +/- 16 mm Hg (p less than 0.05) and total pulmonary resistance from 17.1 +/- 8.7 to 9.7 +/- 5.9 units (p less than 0.005), and increased cardiac output from 4.22 +/- 1.64 to 6.57 +/- 2.04 l/min (p less than 0.01). Heart rate increased from 83 +/- 13 to 94 +/- 11 beats/min (p = 0.1) and mean systemic arterial pressure decreased from 90 +/- 12 to 77 +/- 4 mm Hg (p = 0.055). Three patients who received a continuous infusion of prostacyclin for 24-48 hours had sustained reductions in total pulmonary resistance during the infusion period. These data demonstrate that prostacyclin can increase cardiac output and reduce pulmonary arterial pressure and resistance in PPH.
Divergent effects of inotropic stimulation on the ischemic and severely depressed reperfused myocardium.
Authors: Mercier J C , Lando U , Kanmatsuse K , Ninomiya K , Meerbaum S , Fishbein M C , Swan H J , Ganz W
Published: June 2011

Mechanical function remains depressed for hours and days after even brief periods of ischemia. To determine whether the depressed function of the reperfused myocardium could be improved y inotropic stimulation, we studied segmental function during ischemia and after reperfusion using mercury-in-Silastic length gauges in 15 dogs. During coronary artery occlusion, segmental function could not be improved by inotropic stimulation with dopamine. Release of occlusion after 30 minutes of ischemia resulted in only slight improvement in segmental function (systolic shortening at 20% of control). After reperfusion, segmental function could be markedly enhanced by inotropic stimulation. The response to inotropic stimulation was similar after reperfusion after 3 hours of ischemia if the myocardium remained viable (nine dogs). When the myocardium was necrotic (five dogs), there was no improvement after reperfusion, either spontaneously or in response to inotropic stimulation. If applicable to humans, these results suggest that intractable pump failure caused by extensive but reversible ischemia could be effectively treated by reperfusion and inotropic stimulation.
Electrocardiographic measures of left ventricular hypertrophy in children across the distribution of blood pressure: the Muscatine study.
Authors: Schieken R M , Clarke W R , Prineas R , Klein V , Lauer R M
Published: June 2011

We sought to test the effectiveness of the ECG as a measure of increased left ventricular wall mass in children with high blood pressure. One hundred eighty-one children, ages 9-18 years, were selected from the lowest, middle and highest quintile of systolic blood pressure from the Muscatine Study, based upon two biennial school screenings. After correction for age, sex, height, weight and skinfold thickness, children with the highest blood pressure had increased echocardiographic left ventricular wall mass (p less than 0.02). Voltage measurements of maximum R and S waves in the standard and precordial leads were measured by computer. We correlated blood pressure and echocardiographic measurements of the interventricular septum, left ventricular posterior wall and left ventricular wall mass to electrocardiographic combinations used to predict left ventricular hypertrophy in both children and adults. The electrocardiographic correlations ranged from -0.01 to + 0.17. Poor correlations were found between electrocardiographic measures and blood pressure, left ventricular wall thickness or left ventricular wall mass. Skinfold thickness and weight had negative correlations, suggesting a damping effect upon measured voltage. We conclude that the echocardiogram is a more sensitive measurement of increased left ventricular mass than the ECG in children with elevated blood pressure.
Comparison of techniques for measuring baroreflex sensitivity in man.
Authors: Goldstein D S , Horwitz D , Keiser H R
Published: June 2011

Because discrepancies about baroreflex sensitivity in essential hypertension may have resulted from the use of different measurement techniques, we assessed the extent to which the results of different techniques agree in the same subjects. The eight techniques studied were the change in RR interval per unit change in systolic pressure during the Valsalva maneuver, upon release of the Valsalva maneuver, after injection of phenylephrine and after injection of nitroglycerin; the changes in RR interval and in systolic pressure per mm Hg externally applied neck suction; and the changes in RR interval and systolic pressure per mm Hg externally applied neck pressure. The average intercorrelation among these measures in 30 subjects was statistically significant (r = 0.36, p less than 0.01), but suggests that variance in one measure accounted for an average of about 13% of the variance in other measures. Standard deviations among subjects were often as large as the mean, indicating important interindividual variability as well. These findings demonstrate that baroreflex sensitivity varies widely among subjects and that different techniques for measuring baroreflex sensitivity probably measure different aspects of baroreflex function.
The relationship between ventricular ectopic beat frequency and heart rate.
Authors: Winkle R A
Published: June 2011

We examined the relationship between the frequency of premature ventricle complexes (PVCs) and underlying heart rate in 24 patients with frequent PVCs using 24-hour ambulatory ECG recordings. Plots of PVC frequency vs heart rate were made at 1-beat/min intervals for all heart rates that were recorded for at least 5 minutes of the 24 hours. Heart rates during 24 hours ranged from 56 +/- 10.0 to 102.2 +/- 15.4 beats/min. Twenty-three of the 24 patients had a distinct relationship between PVC frequency and heart rate. Patterns included an approximate log-linear increase in PVCs at higher heart rates in 12 patients, a log-linear decrease (overdrive suppression) in one patient, flat curves in three patients, and a complex relationship (e.g., more PVCs at low rates and suppression at high rates) in seven patients. Patterns were reproducible in 21 of the 24 patients on repeat ambulatory ECG monitorings done 1 day to 2 months later. We conclude that most patients with frequent PVCs have a characteristic relationship between PVC frequency and heart rate over the range of heart rates achieved during routine daily activity. The most frequent relationship is a marked increase in PVC frequency with increasing heart rate. These observations may in part explain such phenomena as "spontaneous" variability of PVC frequency, sleep suppression of PVCs and suppression of PVCs by beta-blocking drugs.
Clinical presentation and natural history of mild discrete subaortic stenosis. Follow-up of 1--17 years.
Authors: Shem-Tov A , Schneeweiss A , Motro M , Neufeld H N
Published: June 2011

We report 21 patients with discrete subaortic stenosis (DSS) causing mild obstruction with a peak systolic left ventricular outflow pressure gradients less than 50 mm Hg. They were followed 1--17 years (mean 6.5 years), and eight were recatheterized before surgery, 2--17 years after the first cardiac catheterization. Three patients (14%) had subacute bacterial endocarditis. Ten (48%) had aortic insufficiency, one of whom had no pressure gradient across the left ventricular outflow tract. In three of the 10 patients, aortic insufficiency was found only at the second catheterization. Nine patients (43%) had hyperactive, asymmetric left ventricular contraction; in three, this finding was present only at the second catheterization. Seven of the eight patients who were recatheterized (33% of the entire group) showed an increase in gradient. The increase was from a mean gradient of 35.2 mm Hg to 76.7 mm Hg. Seventeen patients (81%) had at least one of these four features. In view of these data, we suggest that surgical indications for DSS might be expanded, although definitive recommendations are not possible. All cases of DSS should be carefully followed. Surgery should be performed if signs of progressive complications develop.
Prognostic value of exercise testing, coronary angiography and left ventriculography 6--8 weeks after myocardial infarction.
Authors: De Feyter P J , van Eenige M J , Dighton D H , Visser F C , de Jong J , Roos J P
Published: June 2011

This study provides data on a consecutive series of 179 survivors of acute myocardial infarction (MI) who had symptom-limited treadmill exercise testing, coronary angiography and left ventriculography within 6--8 weeks after infarction. No patient died. The prevalence of multivessel disease was higher in the symptomatic survivors (79%) (p less than 0.001). The prevalence of multivessel disease in inferior MI was 63% and in anterior MI 42% (p less than 0.001). Left ventricular impairment was more severe in anterior and preexisting MI than in inferior and nontransmural MI (p less than 0.005). During a mean follow-up of 28 months, 11 cardiac deaths and 12 reinfarctions occurred. The total mortality rate was 22% (10 of 46) in patients with an ejection fraction less than 30% or three-vessel disease and 1% (one of 133) in patients with an ejection fraction greater than or equal to 30% and one- or two-vessel disease (p less than 0.001). A group at high risk of mortality is thus identified by angiography. The total reinfarction rate was 9% (11 of 121) in patients with an exercise tolerance of less than 10 minutes (Bruce protocol) and 2% (one of 58) in patients with an exercise tolerance of 10 minutes or more (p less than 0.1). The 58 patients who had an exercise tolerance of 10 minutes or more had a very low risk for cardiac death or reinfarction.
Pharmacologic modification of myocardial ischemia.
Authors: Wetstein L , Simson M B , Feldman P D , Harken A H
Published: June 2011

The value of three agents in reducing the area of myocardial ischemia in rabbit hearts perfused with crystalloid solution was examined. Ten hearts received crystalloid solution with methylprednisolone (M), 0.25 mg/ml; 18 with hyaluronidase (H), 4 U/ml; and 10 with propranolol (P), 1 microgram/ml. Thirty-six hearts served as controls. The mitral valves were excised, the hearts were paced at 240 beats/min and a coronary artery was ligated. The ischemic area was evaluated by nicotinamide adenine dinucleotide autofluorescence photography, an intrinsic, high-resolution display of anoxic tissue. The ischemic area was determined by computer from standardized photographs. Myocardial oxygen consumption (MVO2) was determined and photographs were taken before and at 10-minute intervals after ligation. At 60 minutes, each heart was perfused with rhodamine dye and quick-frozen. In hearts treated with M and H, coronary blood flow increased by 151% (51.7 +/- 3 to 77.9 +/- 3 ml/min) and 150% (48.3 +/- 2 to 72.3 +/- 2 ml/min), respectively (p less than 0.001), whereas in hearts treated with U and P, coronary flow decreased at 60 minutes. In the control hearts, the ischemic area did not change between 5 and 40 minutes of ischemia. The ischemic area of H-treated hearts decreased from 136 +/- 4 mm2 to 110 +/- 9 mm2 between the postligation control and the end of the experiment (p less than 0.01). The ischemic area of M-treated hearts decreased from 131 +/- 5 mm2 to 113 +/- 5 mm2 (p less than 0.05). P produced no change in ischemic area (p greater than 0.4). There was no change in the oxygen-diffusion zone of P-treated or control hearts (439 +/- 13 vs 383 +/- 12 mu, p greater than 0.1). The oxygen-diffusion zone between perfused and anoxic tissue in the M and H hearts increased from 383 +/- 12 mu to 861 +/- 76 mu and 681 +/- 62 mu, respectively (p less than 0.001). We conclude that significant volumes of myocardium remain normoxic within nonperfused areas of M-, P- and H-treated hearts.
Myocardial lactate and adenosine metabolite production as indicators of exercise-induced myocardial ischemia in the dog.
Authors: Vrobel T R , Jorgensen C R , Bache R J
Published: June 2011

To determine the value of lactate and the adenosine metabolites inosine and hypoxanthine as indicators of myocardial ischemia, we measured the levels of these metabolites in arterial and coronary sinus blood of nine chronically instrumented dogs subjected to exercise stress before and during reversible circumflex coronary artery occlusion. The degree of circumflex bed hypoperfusion was measured by 15-mu microspheres and the reduction in circumflex coronary flow was measured with a proximal flow probe. Adenosine metabolites, although below the level of accurate detection in our laboratory in arterial blood (i.e., 0.5 microM/l), were detected in coronary sinus blood (range 2.7--18.7 microM/l) in 26 of 33 studies with partial circumflex occlusion when circumflex flow was reduced to less than 80% of that seen during exercise without occlusion and when only subendocardial perfusion was reduced. Global left ventricular flow and transmural flow in nonischemic beds did not correlate with positive studies. Myocardial lactate extraction was a less accurate test for determining circumflex bed hypoperfusion. Thus, myocardial production of adenosine metabolites is a sensitive qualitative test of exercise-induced ischemia responding to a modest fall in coronary flow when only subendocardial hypoperfusion is present.
Survival of medically treated patients in the coronary artery surgery study (CASS) registry.
Authors: Mock M B , Ringqvist I , Fisher L D , Davis K B , Chaitman B R , Kouchoukos N T , Kaiser G C , Alderman E , Ryan T J , Russell R O , Mullin S , Fray D , Killip T
Published: June 2011

The objective of this study was to evaluate the impact on survival of the anatomic extent of obstructive coronary artery disease and of two measures of left ventricular (LV) performance. This study is based on 20,088 patients without previous coronary artery bypass graft surgery who were enrolled in the registry of the National Heart, Lung, and Blood Institute Coronary Artery Surgery Study from 1975 to 1979. The cumulative 4-year survival of medically managed patients was analyzed to determine the survival of specific subsets of patients with obstructive coronary disease. The vital status of 99.8% of the patients was known. The 4-year survival of medically treated patients with no significant obstructive disease was 97%, in contrast to 92%, 84% and 68% in patients with one-, two- and three-vessel disease, respectively. The presence of left main coronary artery disease decreased survival significantly. The 4-year survival decreased from 70% to 60% in patients with three-vessel disease when significant obstruction of the left main coronary artery was also present. Patients with significant coronary artery disease who had an ejection fraction of 50--100%, 35--49%, and 0--34% had a 4-year survival of 92%, 83% and 58%, respectively. The systolic contraction pattern was assessed in five selected segments and given a score of 1--6, with a score of 1 for normal function, increasing to 6 if an aneurysm was present. In a patient with normal LV contraction in all five segments of the LV ventricular angiogram, the LV score would equal 5. Patients with an LV score of 5--11, 12--16 and 17--30 had 4-year survivals of 90%, 71% and 53%, respectively. Patients with good LV function (a score of 5--11) had a 4-year survival of 94%, 91% and 79% for one-, two- and three-vessel disease, respectively. Patients with poor left ventricular function (score of 17--30) had a 4-year survival rate of 67%, 61% and 42% in one-, two- and three-vessel disease, respectively. Thus, LV function is a more important predictor of survival than the number of diseased vessels.
Treatment of stable angina of effort with verapamil: a double-blind, placebo-controlled randomized crossover study.
Authors: Brodsky S J , Cutler S S , Weiner D A , McCabe C H , Ryan T J , Klein M D
Published: June 2011

The effects of verapamil were assessed in 26 patients with stable exertional angina pectoris in a double-blind, placebo-controlled, randomized crossover protocol using serial treadmill tests. Verapamil, 480 mg/day, reduced anginal frequency from 5.6 +/- 7.3 to 2.2 +/- 3.9 attacks per week (p less than 0.001) and nitroglycerin consumption from 3.4 +/- 4.9 to 1.2 +/- 2.5 tablets per week (p less than 0.05) compared with placebo. Treadmill time increased from 6.4 +/- 2.1 minutes during the placebo phase to 7.5 +/- 1.8 minutes during the verapamil phase (p less than 0.001). Verapamil's beneficial effect appeared to be related, in part, to a 10% reduction of the rate-pressure product at rest (p less than 0.05) and a 12% reduction during submaximal exercise (p less than 0.001). Verapamil also caused less marked ST-segment depressions at peak exercise (p less than 0.05) at a similar rate-pressure product, suggesting a favorable redistribution of coronary blood flow to the ischemic zone. Side effects from verapamil were minimal, consisting mainly of constipation (six patients). Verapamil appears to be a safe and effective drug for treating angina of effort.
A double-blind randomized trial of propranolol and verapamil in the treatment of effort angina.
Authors: Sadick N N , Tan A T , Fletcher P J , Morris J , Kelly D T
Published: June 2011

In 18 patients with stable effort angina, verapamil, 80 mg four times daily, was compared with propranolol, 80 mg four times daily, in a double-blind, placebo-controlled trial to assess the effects on anginal threshold, exercise capacity and left ventricular function measured by gated equilibrium blood pool scanning. Both propranolol and verapamil improved exercise capacity (placebo 424 +/- 135 W-min; propranolol 513 +/- 168 W-min, p less than 0.01; verapamil 545 +/- 215 W-min, p less than 0.005) and prolonged the time to 1 mm of ST depression (placebo 4.5 +/- 1.3 minutes; propranolol 7.4 +/- 1.4 minutes, p less than 0.005; verapamil 6.6 +/- 1.9 minutes, p less than 0.005). At rest, the mean left ventricular ejection fraction did not change significantly during drug therapy (placebo 57 +/- 13%, propranolol 55 +/- 12%, verapamil 55 +/- 13%). While taking placebo, all 18 patients had a decrease in exercise ejection fraction. In contrast, 12 patients taking propranolol and 14 patients taking verapamil had a 5% or greater increase in ejection fraction during exercise. Verapamil is an effective primary therapy and a satisfactory alternative to propranolol in patients with stable effort angina.