bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification and abolition of re-entry within the His-Purkinje system in man by diphenylhydantoin.
Authors: Dhatt M S , Akhtar M , Reddy P , Gomes J A , Lau S H , Caracta A R , Damato A N
Published: June 2012

The phenomenon of macrore-entry (Re) within the His-Purkinje system (HPS) was consistently observed in 10 of 19 patients during retrograde refractory period studies. Effects of intravenous infusion of diphenylhydantoin (DPH) on Re were studied in these 10 patients 10 minutes after completion of infusion (mean plasma level equal to 17.0 microgram/ml). Diphenylhydantoin modified determinants of Re in seven patients (group I) and abolished Re in the remaining three patients (group II). In group I, DPH shortened the critical V1 V2 from 310.0 +/- 30.5 to 292.9 +/- 25.6 msec (P less than 0.025) and critical V2 H2 intervals for Re from 201.4 +/- 18.4 to 185.0 +/- 13.8 msec (P greater than 0.05). In group II, DPH abolished Re in two of three patients by precluding attainment of critical V2 H2 intervals whereas Re was abolished in the remaining one patient despite attainment of critical V2 H2 intervals (vs control). For both groups, DPH significantly shortened functional and effective refractory periods of the HPS (P less than 0.001 and less than 0.01, respectively) without significantly affecting the effective refractory period of the ventricular muscle. Diphenylhydantoin either completely abolished or significantly shortened the retrograde gap zones in the HPS. It is concluded that diphenylhydantoin significantly shortens His-Purkinje system refractoriness, abolishing Re in the patients with higher degree of improvement in refractoriness.
Transthoracic ventricular defibrillation in the 100 kg calf with unidirectional rectangular pulses.
Authors: Gold J H , Schuder J C , Stoeckle H , Granberg T A , Hamdani S Z , Rychlewski J M
Published: June 2012

The effectiveness in reversing ventricular fibrillation of 30 seconds duration of unidirectional rectangular-wave shocks having pulse widths of 0.5 through 64 msec, pulse amplitudes of 35, 50, 70, 100, and 140 amp, and pulse energies of 109 through 1,660 J was studied in 3,303 transthoracic fibrillation-defibrillation episodes in 100 kg calves. A total of 38 animals were used in the study. Postdefibrillation electrocardiograms were recorded. Families of curves of percent successful defibrillation vs pulse duration, percent successful defibrillation vs pulse energy, duration of postdefibrillation complete block or standstill vs energy, and time required for a return to normal sinus rhythm vs energy were derived. The most effective waveform studied (70 amp--8 msec--862 J) yielded defibrillation on the initial attempt in 93% of 120 episodes. In general, the duration of complete block or standstill and the time required for a return to normal sinus rhythm increased with increasing pulse current and pulse energy.
Mean velocity of circumferential fiber shortening in prolapsed mitral leaflet syndrome.
Authors: Pisano D , Cha S D , Gooch A S , Maranhao V , Goldberg H
Published: June 2012

In 26 patients with mitral valve prolapse, ventricular function was evaluated by mean velocity of circumferential fiber shortening (MVCF) as measured along the basilar, middle and apical axes. Significantly increased rates of MVCF were found in patients with mitral prolapse along the basilar axis (1.75 +/- 0.23 circ/sec) and middle axis (2.09 +/- 0.34 cir/sec) (P less than 0.025 and P less than 0.05, respectively). Patients with mitral valve prolapse and regurgitation demonstrated a significant increase in MVCF along the basilar axes (1.72 +/- 0.15 cir/sec) (P less than 0.05). Asynergy apperars to have a negative effect on the MVCF along the middle axis. The MVCF was found not to be related to clinical findings, symptoms or electrocardiographic changes. The mechanism for the increase in MVCF in patients with mitral valve prolapse remains unsettled.
The aortic closure sound in pure aortic insufficiency.
Authors: Sabbah H N , Khaja F , Anbe D T , Stein P D
Published: June 2012

The second sound in aortic insufficiency has been described as accentuated, normal, or moderately diminished. A study of intracardiac phonocardiograms was performed to evaluate its intensity and to eliminate extracardiac factors. Pressure and intracardiac sound measurements were made in 28 patients undergoing diagnostic cardiac catheterization. Recordings were obtained above the aortic valve and within the left ventricle in 14 patients with normal aortic valves and 11 patients with aortic insufficiency uncomplicated by aortic stenosis. The amplitude of the aortic closure sound in the patients with pure aortic insufficiency, 1000 +/- 100 dynes/cm2, was significantly lower than in those patients with normal aortic valves, 3100 +/- 200 dynes/cm2 (P less than 0.001). The results indicate, therefore, that the presence of aortic insufficiency causes a diminished amplitude of the aortic closure sound. These results are supportive of the theory that the second heart sound is caused by diastolic vibrations of the closed aortic cusps. Diminished valvular vibrations and sound would occur in pure aortic insufficiency if the valve is unable to properly tense during diastole, or if the rate of development of the driving pressure is diminished.
Consumption coagulopathy and microangiopathic hemolytic anemia with an axillo-femoral graft.
Authors: Myers T J , Hild D H
Published: June 2012

Consumption coagulopathy and microangiopathic hemolytic anemia occurred as a complication of insertion of an axillofemoral, preclotted dacron graft. Treatment with heparin followed by dipyridamole and aspirin normalized the hematologic and coagulation abnormalities over a two month period. The mechanism of consumption coagulopathy associated with prosthetic grafts is discussed and a possible role for treatment with antiplatelet agents is suggested.
Analysis of left ventricular function from multiple gated acquisition cardiac blood pool imaging. Comparison to contrast angiography.
Authors: Burow R D , Strauss H W , Singleton R , Pond M , Rehn T , Bailey I K , Griffith L C , Nickoloff E , Pitt B
Published: June 2012

Global ventricular function was evaluated by both multiple gated cardiac blood pool scans (MUGA) and contrast ventriculograms in a group of 17 patients with suspected coronary artery disease. The contrast ventriculograms were analyzed frame by frame to generate a volume versus time curve for each patient, while the tracer data were analyzed by two methods: 1) the standard method, in which the left ventricle is identified on the end-diastolic frame and the background corrected activity under the region of interest obtained from the entire cardiac cycle, and displayed as a time versus activity curve; and 2) by a semi-automatic method in which the computer applies a threshold detection program to define the ventricular borders, and activity in the chamber at each point in the cardiac cycle is defined after background correction. The tracer data in each patient were analyzed independently by four observers. The tracer data correlated with the contrast data on a point by point basis r = 0.87 for the standard method, and 0.93 for the semi-automatic technique. An F test of variance revealed the semi-automatic method superior to the standard approach (P less than 0.05).
Axial cineangiography in congenital heart disease. Section II. Specific lesions.
Authors: Elliott L P , Bargeron L M , Bream P R , Soto B , Curry G C
Published: June 2012

The value of axial cineangiography in several forms of congenital heart disease serves as an illustrated supplement to Section I. These techniques visualize defects in the entire ventricular and atrial septum. In persistent atrioventricular (A-V) canal, it is possible to visualize all parts of both septa, status of the A-V valves (two valves versus a common A-V valve), and if a common A-V valve, its degree of override. In tetralogy of Fallot, the bifurcation of the pulmonary trunk, entire ventricular septum and coronary arteries are vividly shown. The presence of true and confluent pulmonary arteries versus systemic or bronchial arteries in pseudotruncus is clearcut. In double outlet right ventricle or in transpositions with or without double outlet right ventricle, the mitral valve-semilunar valve relationships, the left ventricular outflow tract, subpulmonary region and a straddling tricuspid valve are well demonstrated. In asymmetric septal hypertrophy, biventricular angiography may be circumvented.
Occult constrictive pericardial disease. Diagnosis by rapid volume expansion and correction by pericardiectomy.
Authors: Bush C A , Stang J M , Wooley C F , Kilman J W
Published: June 2012

Significant pericardial disease can exist without overt manifestations. Occult constrictive pericardial disease (OCPD) is identified by normal baseline hemodynamics and normal left ventricular systolic function with a characteristic response to rapid volume infusion. Following the intravenous administration of 1000 ml of normal saline over six to eight minutes, striking elevations of filling pressures are seen; however, diagnosis depends specifically upon a) the development of typical pressure pulse morphology of constriction, b) loss or reversal or respiratory variation of right atrial pressure, and c) precise diastolic equilibration of intracardiac pressures. Nineteen patients with OCPD have been identified in a five year period. Unexplained fatigue, dyspnea and chest pain was the uniform pattern of presentation. Eleven have undergone pericardiectomy resulting in a dramatic symptomatic improvement in all. Each demonstrated gross and/or microscopic evidence of pericardial disease. Recatheterization with volume infusion in five patients following pericardiectomy has revealed return to normal or near normal hemodynamics. This study describes the method for diagnosis of OCPD and recommends pericardiectomy for the management of disabling symptoms.
Cardiovascular function during early recovery from acute myocardial infarction.
Authors: Wohl A J , Lewis H R , Campbell W , Karlsson E , Willerson J T , Mullins C B , Blomqvist C G
Published: June 2012

Fifty patients with acute myocardial infarction were studied serially to evaluate the extent and nature of functional cardiovascular impairment and the time course of recovery. Reinfarction or death occurred in six patients. Peak workload during bicycle exercise in a subgroup of 25 patients with maximal initial test and complete follow-up increased from 334 to 409 kpm/min (P less than 0.01) bwtween three and six weeks. There was further significant (P less than 0.01) improvement between three and six months from 438 to 488 kpm/min. The incidence of ischemia at a constant workload decreased between three and six weeks without any significant changes in heart rate or blood pressure. Mean cardiac output during exercise at three months was 6.5 and at six months 7.8 L/min (P less than 0.05). Corresponding values for stroke volume were 61 and 72 ml (P less than 0.05). The data suggest that in clinically stable patients there is an early improvement of the relation between myocardial oxygen supply and demand and a late improvement of functional capacity associated with increased stroke volume and cardiac output.
Influence of reduction of preload and afterload by nitroglycerin on left ventricular diastolic pressure-volume relations and relaxation in man.
Authors: Ludbrook P A , Byrne J D , Kurnik P B , McKnight R C
Published: June 2012

To clarify the mechanisms of afterload reduction on left ventricular diastolic function, the influence of nitroglycerin upon ventricular diastolic pressure-volume relations was studied in 22 patients during catheterization. After nitroglycerin, average ventricular systolic pressure declined by 25 mm Hg (18%) and end-diastolic pressure by 7 mm Hg (28%) (P less than 0.005). End-systolic and diastolic ventricular volumes decreased by 37% and 23% respectively (P less than 0.005). Although peak negative dP/dt fell by 22% (P less than 0.0005), "T", an index of the time course of isovolumic diastolic ventricular relaxation, was insignificantly changed. Diastolic pressure-volume curves were significantly displaced downward and leftward without significant change in slope, suggesting that a family of pressure-volume curves for each ventricle with similar slope but positions depend upon immediate loading conditions. Absence of change in slope or of "T" suggests that this displacement may be mediated indirectly, perhaps by relaxation of extracardiac constraints to ventricular distensibility. Accordingly, improvement in ventricular function by vasodilators may be partly due to downward displacement of the pressure-volume relation, with associated reduction of wall tension and myocardial oxygen consumption.
A mathematical model of parasystole and its application to clinical arrhythmias.
Authors: Moe G K , Jalife J , Mueller W J , Moe B
Published: June 2012

A ventricular parasystolic focus capable of generating manifest ectopic beats should not be totally insulated from the electrical events that accompany depolarization in the surrounding tissue; the intrinsic cycle length of the ectopic discharge may be modulated by electrotonic influences transmitted across the zone of "protection." To study the nature of the interaction, response patterns were examined in a mathematical model programmed to simulate an ectopic pacemaker protected, but not divorced from ventricular responses to the normal pacemaker. Computer runs covered a wide range of heart rates, and a wide range of magnitudes of the simulated electrotonic influence. Application of the results obtained in the model to published examples of complex arrhythmias revealed a remarkably close fit to many clinical examples. This findings suggests that many patterns attributed to a re-entrant "extrasystolic" rhythm may, in fact, represent the modulated activity of a parasystolic focus.
Efficacy of propranolol in the control of exercise-induced or augmented ventricular ectopic activity.
Authors: Nixon J V , Pennington W , Ritter W , Shapiro W
Published: June 2012

The effect of propranolol on exercise-induced or augmented ventricular ectopy was studied in sixteen male patients, six of whom had documented coronary artery disease. Fifteen patients were exercised after two weeks of oral therapy, fourteen after single oral therapy and eight patients after intravenous therapy. Propranolol dosage was titrated to produce maximal beta-adrenergic blockade. Effective reduction of exercise-induced ventricular ectopy occurred in ten of fifteen patients (P less than 0.001), and in five of six patients with coronary disease (P less than 0.02). Propranolol therapy abolished ventricular couplets in eight of twelve patients and ventricular tachycardia in four of the patients. Single oral and intravenous therapy had similar or greater effects. Plasma propranolol levels following different routes of administration did not correlate with exercise-induced maximal heart rates or percent reduction in ventricular ectopy. When compared to exercise in eleven patients, ambulatory monitoring underestimated the severity, particularly the highest grades, of ventricular ectopy.
Effect of phasic respiration on left ventricular dimension and performance in a normal population. An echocardiographic study.
Authors: Brenner J I , Waugh R A
Published: June 2012

Echocardiographic examination of the left ventricle (LV) in 30 normal subjects, 5 to 47 years of age, was performed in order to analyze the effects of phasic respiration on LV dimensions and derived LV function. Peak expiratory and peak inspiratory LV diastolic and systolic dimensions were measured and extrapolated to volume estimates using a standard formula. Although there was wide variation in the individual measurements, and particularly in systolic dimension, the mean peak inspiratory diastolic dimension, derived diastolic volume, and stroke volume all decreased significantly (P less than 0.001); a smaller decrease in ejection fraction was seen (P less than 0.02), while the changes in mean end-systolic dimension and end-systolic volume were not significant. While these observed changes may reflect a true physiologic variation, an artifactual component cannot be excluded. Regardless of their physiologic significance, however, these data show that the effect of phasic respiration is a factor to be considered in correlative echocardiographic studies of LV function in both normal and, possibly, pathologic cardiovascular conditions.
The role of the exercise test in the evaluation of patients for ischemic heart disease.
Authors: McNeer J F , Margolis J R , Lee K L , Kisslo J A , Peter R H , Kong Y , Behar V S , Wallace A G , McCants C B , Rosati R A
Published: June 2012

A cohort of 1472 patients who underwent both exercise stress testing and coronary angiography within six weeks was examined. The data indicated that a combination of exercise parameters is both diagnostically and prognostically important. Almost all patients (greater than 97%) who had positive exercise tests at Stage I or Stage II had significant coronary artery disease. More than half of these (greater than 60%) had three vessel disease and over 25% had significant narrowing (greater than 50%) of the left main coronary artery. Patients who achieved Stage IV or greater exercise durations with either negative or indeterminate ST-segment response had less than a 15% prevalence of three vessel disease and less than a 1% prevalence of left main coronary artery disease. A low risk subgroup (75% of all non-operated patients) was identified with a twelve month survival greater than 99%. A high risk subgroup (11% of all nonoperated patients) was identified with a twelve month survival of less than 85%. The exercise test is a noninvasive, reproducible method to assess the presence and extent of anatomic disease and the prognosis when significant disease has been defined. It should be used in conjunction with other noninvasive tests to determine optimal management in patients evaluated for ischemic heart disease.
Prolonged atrial conduction. A major predisposing factor for the development of atrial flutter.
Authors: Leier C V , Meacham J A , Schaal S F
Published: June 2012

Electrophysiological studies were performed during sinus rhythm on 21 patients who had demonstrated the spontaneous occurrence of sustained atrial flutter. The purpose was to determine if atrial conduction disease is a prediposing factor for the development of atrial flutter. Patients with atrial enlargement were excluded from the series. The control group consisted of 11 age-matched patients with normal electrocardiograms and electrophysiology studies. The flutter group showed prolongation of the mean right intra-atrial conduction time at 50 msec (control of 37 msec, P less than 0.05), the mean interatrial conduction time at 92 msec (control of 44 msec, P less than 0.001) and the mean P wave duration at 132 msec (control of 112 msec, P less than 0.01). The flutter group also demonstrated a higher incidence of sinus node dysfunction and ventricular conduction disease compared to the control group. These data indicate that patients who develop atrial flutter have atrial conduction disease. Atrial conduction disease appears to be 1) a major prediposing factor for the development of atrial flutter and 2) a part of the fibro-degenerative conduction disease spectrum.
Cardiac structure growth pattern determined by echocardiography.
Authors: Rogé C L , Silverman N H , Hart P A , Ray R M
Published: June 2012

Using M-mode echocardiography, we measured dimensions of the ventricular walls and cavities, great vessels, and left atrium and atrioventricular valve excursions on 93 infants and children without heart disease. The data were analyzed by relating each dimension in mm to body surface area in m2 and the 90% tolerance limits for the data were calculated. The tolerance lines of the data were wider than previously recorded. At birth and maturity they were similar to the range defined as normal by studies in neonates and adults. We suggest that the tolerance lines of these normal data may be used for quantitative echocardiography in childhood.
Combined double chambered right ventricle and discrete subaortic stenosis.
Authors: Baumstark A , Fellows K E , Rosenthal A
Published: June 2012

Nine cases of combined double-chambered right ventricle (DCRV) and discrete subaortic stenosis (DSAS) are presented. A review of 1077 consecutively catheterized patients indicates an association of these two uncommon anomalies nine times greater than expected. One or both obstructive lesions may be hemodynamically significant and require surgery. Whenever DCRV or DSAS is suspected or identified, the cardiac catheterization should include studies of both the right and left ventricles.
The prognostic implications of acute myocardial infarct scintigraphy with 99mTc-pyrophosphate.
Authors: Holman B L , Chisholm R J , Braunwald E
Published: June 2012

The predictive value of the myocardial scintigraphy with 99mTc-pyrophosphate was studied in 100 patients admitted to the coronary care unit with suspected acute myocardial infarction. None of the 21 patients with normal scintigrams had acute myocardial infraction by other criteria. Fifty-five percent of patients with diffuse uptake (pattern B), 73% of patients with focal uptake (pattern C) and all patients with intense focal uptake (pattern D) and massive uptake (pattern E) had acute infarction. The complication rate in the hospital and after discharge (mean followup: 6.1 months) for patients with pattern E was 88% compared to 42% for D, 30% for C, 36% for B and 10% for patients with normal scintigrams (A). For patients with acute infarction with patterns C, D and E, the complication rate rose with increasing size of the myocardial uptake of 99mTc-pyrophosphate. In addition to its diagnostic potential, scintigraphy provides prognostic information which is useful for patient triage and for therapeutic decisions early in the evolution of the infarct.
Early redistribution of thallium-201 after temporary ischemia.
Authors: Schwartz J S , Ponto R , Carlyle P , Forstrom L , Cohn J N
Published: June 2012

To define the time course of redistribution of thallium-201 (201Tl), ischemia was induced in seven pigs by temporary occlusion of the circumflex coronary artery. After 1 1/2 min of occlusion 201Tl and labeled microspheres were injected into the left atrium. Flow was re-established 4 min after occlusion. Prior to reflow, the relative activities of 201Tl and microspheres in the ischemic area were similar, but as early as 5 min after reflow the relative 201Tl activity was considerably higher than the relative microsphere activity and from 15 to 105 min after reflow, relative 201Tl activity (averabe 69% of that in normal myocardium) continued to be higher than relative microsphere activity (average 6% of normal). Myocardial arteriovenous differences for 201Tl were followed sequentially after 201Tl injection in normal dogs and in dogs with temporary coronary occlusions. The results suggested both loss of 201Tl from normal myocardium beginning 10 min after 201Tl injection and increased extraction of 201Tl from the blood pool immediately after release of a transient occlusion. Redistribution of 201Tl therefore begins very soon after relief of myocardial ischemia and even a short delay in initiating myocardial imaging may decrease the sensitivity of the technique for detecting transient ischemia.
Blood volume prior to and following treatment of acute cardiogenic pulmonary edema.
Authors: Figueras J , Weil M H
Published: June 2012

Following onset of acute cardiogenic pulmonary edema in 21 patients, increases in hematocrit, plasma protein concentration, and colloid osmotic pressure were associated with decreases in plasma volume. Accordingly, there was a loss of hypo-oncotic fluid into the extravascular spaces. Following treatment with oxygen, furosemide, and morphine sulfate and reversal of clinical and radiographic signs of pulmonary edema, declines in hematocrit, plasma protein concentration, and colloid osmotic pressure were associated with increases in plasma volume. Hypo-oncotic edema fluid was therefore reabsorbed into the vascular compartment. The concept that acute heeart failure with pulmonary edema is associated with an increase in intravascular volume is therefore not supported. To the contrary, there is a reduction of blood volume during acute pulmonary edema. During reversal of acute pulmonary edema with diuresis, there was re-expansion rather than contraction of blood volume.
Reduction of coronary blood flow during coronary artery spasm occurring spontaneously and after provocation by ergonovine maleate.
Authors: Ricci D R , Orlick A E , Doherty P W , Cipriano P R , Harrison D C
Published: June 2012

A 50-year-old man suffering from recurrent chest pain accompanied by transient ST-segment elevation developed spasm of the left anterior descending coronary artery after receiving ergonovine maleate. During spontaneous chest pain, thermodilution coronary sinus blood flow fell from 96 ml/min to 46 ml/min, while the coronary sinsu arteriovenous oxygen difference widened from 9.82 volumes percent to 11.3 volumes percent. During spontaneous relief of pain, coincident with resolution of the ST-segment changes, coronary sinus blood flow gradually rose to 135 ml/min, while coronary sinus arteriovenous oxygen difference narrowed to 6.82 volumes percent. Similar aterations in coronoary sinus blood flow accompanied chest pain provoked by ergonovine maleate. A thallium-201 scan confirmed a perfusion defect in the distribution the left anterior descending coronary artery. Thus, coronary artery spasm can produce a marked deficity in coronary blood flow that is associated with increased myocardial oxygen extraction; release of spasm creates a hyperemic response.
Beneficial effect of physical training on blood flow to myocardium perfused by chronic collaterals in the exercising dog.
Authors: Heaton W H , Marr K C , Capurro N L , Goldstein R E , Epstein S E
Published: June 2012

To determine the effect of physical training on collateral blood flow, we measured regional myocardial blood flow (MBF) by injecting 15 mu radioactive microspheres at rest and during exercise in 14 dogs with chronic coronary occlusive lesions. Seven dogs subsequently trained for 6 weeks while the other seven remained in kennels. Training effect was documented by decrease in heart rate during exercise that averaged 35 beats/min. MBF studies were repeated after 6 weeks. Myocardial samples were obtained from normally perfused zones (NZ) and from regions supplied via collaterals (collateral dependent zones or CZ). Initially, endocardial blood flow in CZ averaged 1.110 ml/min/g (83% of NZ, P less than 0.05) at rest and 1.36 ml/min/g (69% of NZ, P less than 0.05) during exercise, indicating relative underperfusion. Epicardial blood flow was equal in NZ and CZ. After 6 weeks MBF was not significantly changed in control animals. After training, however, MBF to underperfused endocardium of CZ during exercise was 39% greater than it had been prior to training. The epicardial portion of CZ (not exhibiting underperfusion) showed no change in MBF during exercise after training. Our data suggest that beneficial effects of training in coronary disease may include improvement in MBF to underperfused collateral-dependent portions of myocardium.
Echocardiographic diagnosis of ruptured aortic valve leaflet in bacterial endocarditis.
Authors: Ramirez J , Guardiola J , Flowers N C
Published: June 2012

Aortic valve rupture, secondary to aortic valve endocarditis, was diagnosed echocardiographically and closely followed preoperatively. The ruptured left coronary cusp of the aortic valve was seen as dense irregular echoes, located anteriorly during ventricular diastole, and protruding into the left ventricular outflow tract in an otherwise normally appearing aortic valve. These echocardiographic findings, when correlated with changes in the clinical status of the patient, prompted immediate cardiac catheterization and aortic valve replacement. Early echocardiographic detection of abnormal aortic cusps and variation from normal aortic root echo features should alert the physician to proceed to cardiac catheterization, and aortic valve replacement if necessary.
Continuous local electrical activity. A mechanism of recurrent ventricular tachycardia.
Authors: Josephson M E , Horowitz L N , Farshidi A
Published: June 2012

Although the mechanism of most episodes of recurrent ventricular tachycardia (VT) is believed to be re-entry, definitive proof of this hypothesis has heretofore been unavailable in man. Using programmed stimulation and ventricular endocardial mapping we studied three patients in whom the initiation of VT was dependent upon developing a critical degree of fractionation and delay in local left ventricular electrograms. When electrical activity spanned diastole, VT ensued. Maintenance of VT was associated with continuous electrical activity resembling "local fibrillation" while termination of VT required cessation of this continuous activity. During sinus rhythm the electrogram recorded from the areas which subsequently developed continuous activity showed markedly fractionated and prolonged electrical activity exceeding 100 msec in duration. We feel these observations of the temporal relationship of continuous activity with the development of VT represent the first documentation of the re-entrant nature of this arrhythmia in man.
Accuracy of echocardiography in assessing left ventricular dimensions and volume.
Authors: Bhatt D R , Isabel-Jones J B , Villoria G J , Nakazawa M , Yabek S M , Marks R A , Jarmakani J M
Published: June 2012

The accuracy of determining left ventricular function from echocardiography was assessed in 26 children (group I) with cineangiographically-determined normal left ventricular volume (LVV) and 28 children (group II) with large left ventricular volumes. Conventional LV echo dimensions were compared to the cineangiographic LV anterior-posterior minor axis (LVmA) and LVV. Very good correlations were found in group I between LV end-diastolic echo dimensions (LVEDD) and cine LVmA (r = 0.91) and between LVEDD and LV end-diastolic volume (LVEDV) by cine in group I (r = 0.86). In group II correlations were less accurate between LVEDD and diastolic LVmA and between LVEDD and LVEDV. There was poor correlation between the cine and echo percent of shortening (r = 0.41) and velocity of circumferential fiber shortening (VCF) (r = 0.51). This study demonstrates that M-mode echocardiography is a very useful method for determining LV dimensions in children with normal LV volume, but is less accurate in children with left ventricular volume overload or with abnormal septal orientation or postoperative status after ventriculotomy.
Relationships among ventricular arrhythmias, coronary artery disease, and angiographic and electrocardiographic indicators of myocardial fibrosis.
Authors: Califf R M , Burks J M , Behar V S , Margolis J R , Wagner G S
Published: June 2012

This study was performed to determine the relationships among angiographic, hemodynamic, clinical, and electrocardiographic data and premature ventricular contractions (PVCs). Arrhythmias were analyzed by 24 hour Holter monitor in 244 patients evaluated for chest pain by coronary angiography and left ventriculography. Using a categorical linear model, the presence of myocardial fibrosis as indicated by both abnormal left ventricular contraction (LVC) and abnormal initial QRS on electrocardiogram was found to be the only independent predictor of both frequent and complex ventricular arrhythmias (P less than .0001). All other descriptors, including the number of diseased vessels (greater than or equal to 75% obstruction), were dependent upon abnormal LVC in their association with PVCs. When the right anterior oblique view of the left ventriculogram was divided into nine segments to allow automated quantiative analysis of LVC, the prevalence of frequent PVCs was directly related to the number of abnormally contracting segments. Of patients with 0 abnormal segments, 11% had greater than or equal to 2 PVC/hr, in contrast to 44%, 73% and 100% of patients with 1-3, 4-6, and 7-9 abnormal wall segments, respectively (P less than 0.01). A similar quantitative relationship was found between premature ventricular contractions and abnormal initial forces indicating previous myocardial infarction on the electrocardiogram.
Verapamil in the management of supraventricular tachyarrhythmias occurring after a recent myocardial infarction.
Authors: Hagemeijer F
Published: June 2012

In 16 patients, a sustained supraventricular tachyarrhythmia occurring less than 72 hours after the first symptom of an acute myocardial infarction was treated with titrated doses of verapamil. The drug was given intravenously in 1 mg increments every minute under continuous monitoring of electrocardiogram and blood pressure. Endpoints for the administration of verapamil were the following: reversion to sinus rhythm; a ventricular rate slower than 100/min; hypotension; a pulmonary capillary wedge pressure rising above 15 mm Hg; signs of intolerance; a maximum dose of 20 mg. Reversion to sinus rhythm was observed in 7/8 patients in atrial flutter and in 1/8 patients in atrial fibrillation; in all the ventricular rate could be slowed below 100/min without untoward effects.
The "false negative" treadmill exercise test and left ventricular dysfunction.
Authors: Kramer N , Susmano A , Shekelle R B
Published: June 2012

One hundred and fifteen consecutive symptomatic patients undergoing graded exercise testing, selective coronary angiography and left ventriculography were retrospectively evaluated. The sensitivity, specificity, and false negative response rates of the exercise tests were 79%, 81%, and 21%, respectively. Although the magnitude of a positive ST-segment response was related to more extensive vascular disease, the frequency of false negative responses was nearly identical in patients with single, double, or triple vessel disease (22%, 21%, 19%). Analysis of the false negative group demonstrated significant ventriculographic and hemodynamic abnormalities when compared to the true positive responders. Five out of six patients with the most serious motion disorders in the study fell into the false negative group. There were no significant differences in the extent, distribution and severity of vascular involvement, or in the development of collateral circulation in the two groups. However, occluded vessels supplied abnormal ventricular segments more frequently in the false negative group (88% vs 38%); the absence of an "ischemic response" and the presence of segments of abnormal myocardium may be related. Left ventricular dysfunction appears to be an important reason for a false negative response to exercise.
Aschoff bodies at necropsy in valvular heart disease. Evidence from an analysis of 543 patients over 14 years of age that rheumatic heart disease, at least anatomically, is a disease of the mitral valve.
Authors: Roberts W C , Virmani R
Published: June 2012

Among 543 necropsy patients over age 14 years with severe chronic valvular heart disease, Aschoff bodies were found in 11 patients (2%). The ages of the 11 patients ranged from 18 to 68 years (avg. 38), and nine had had a history of acute rhematic fever earlier in life. Clinically, nine of the 11 patients had mitral stenosis with or without dysfunction of one or more other cardiac valves, one had isolated aortic regurgitation, and one had both mitral and aortic regurgitation. All 11 patients had diffuse fibrous thickening of the mitral valve leaflets, and all but one had diffuse anatomic lesions of at least one other cardiac valve. No patient with anatomic lesions limited to the aortic valve had Aschoff bodies. Thus, among patients with chronic valvular heart disease, Aschoff bodies, the only anatomic lesion pathognomonic of rheumatic heart disease, indicate diffuse anatomic lesions of the mitral leaflets and usually also anatomic lesions of one or more other cardiac valves. The functional mitral lesion is usually stenosis.
Energy requirement for defibrillation of a markedly overweight patient.
Authors: DeSilva R A , Lown B
Published: June 2012

Recommendations have been made recently that the energy output of present-day defibrillators be increased above the 400 wsec limit. These recommendations are based largely on experimental studies in animals. We report a case of a man weighing 190.1 kg (418.2 lb), successfully resuscitated with a single 400 wsec shock after a prolonged episode of ventricular fibrillation. The observation in this patient as well as data derived from cardiovascular experience indicates that weight is not a significant factor in the successful outcome following defibrillation in adults. Many variables primarily related to the clinical condition of the heart influence the results of countershock. There are no valid studies at present to support the claim that high-energy defibrillators are necessary. In fact, implementation of such a recommendation is premature and possibly dangerous.
The effects of short-term venous congestion on forearm venous volume and reactive hyperemia blood flow in human subjects.
Authors: Zelis R , Capone R , Mansour E , Field J M
Published: June 2012

Congestive heart failure is associated with a reduction in limb venous volume at an effective venous pressure of 30 mm Hg (VV[30]). Further, an attenuated arteriolar dilation in response to a metabolic stimulus has been demonstrated. It was the purpose of this study to determine to what extent the chronic elevation in venous pressure seen in heart failure might explain these abnormalities of the limb circulation. Ten normal human volunteers were subjected to venous congestion of one arm for three hours at 70 mm Hg. A mercury-in-rubber strain gauge plethysmograph was used to measure forearm VV [30] and forearm blood flow at rest after release of five minutes of arterial occlusion (the reactive hyperemia response). Congestion reduced VV [30] 22%, resting forearm blood flow 49% and peak reactive hyperemia blood flow 25%. Thus, chronic venous congestion per se may significantly reduce limb venous volume as well as resting and reactive hyperemia blood flow.
Exercise-induced reduction in myocardial infarct size after coronary artery occlusion in the rat.
Authors: McElroy C L , Gissen S A , Fishbein M C
Published: June 2012

Chronic exercise (E) has been thought to be beneficial to the cardiovascular system by increasing energy production and utilization, improving myocardial contractility and increasing myocardial vascularity; whether or not any of these effects are beneficial to ischemic myocardium is uncertain. In this study, rats were forced to swim one hr/day, 5 days/wk for 5 weeks. They were sacrificed and the myocardial capillary bed was perfused with carbon black. Using a calibrated eyepiece grid, histologic sections of heart were examined to determine capillary/fiber ratios (C/F) and myocardial fiber diameter. C/F was increased by 30% in E rats [0.87 +/- 0.06 (mean +/- SE) (N = 4 rats)] when compared with sedentary controls (C) [0.67 +/- 0.04 (N = 4 rats), P is less than 0.05]. This training effect occurred in the absence of hypertrophy since there were no differences in ventricular weight (1.21 +/- 0.04 mg in E rats vs 1.16 +/- 0.03 mg in C rats) or in fiber diameter (13.0 +/- 0.2 mu in E rats vs 13.1 +/- 0.2 mu in C rats) in the two groups. An additional 27 E rats and 25 C rats underwent left coronary artery occlusion and were sacrificed 48 hr later. Myocardial infarct size was measured by planimetry of histologic sections of serial slices of left ventricle (LV). In the 27 E rats, 21.5 +/- 1.9% of the LV was infarcted compared with 31.3 +/- 2.6% in the 25 C rats (P is less than 0.005). Thus, infarct size was reduced by 30% in E rats. In the rat, exercise results in a reduction of myocardial infarct size after coronary artery occlusion which, at least in part, may be related to increased myocardial vascularity.
Right and left ventricular volume characteristics in common atrioventricular canal.
Authors: Thanopoulos B D , Fisher E A , DuBrow I W , Hastreiter A R
Published: June 2012

Right (RV) and left (LV) ventricular volume characteristics were determined from biplane cineangiography in 29 patients with atrioventricular canal (AVC). The patients were classified into two groups: group I (N = 19), uncomplicated AVC; group II (N = 10), AVC associated with RV obstruction. In group I, LV end-diastolic volume (EDV) [177 +/- 9 (SEM)% of normal] and RVEDV (125 +/- 9%) both were greater than normal (P is less than 0.001 and less than 0.01, respectively). LV ejection fraction (EF) was decreased (0.59 +/- 0.02, P is less than 0.001) but RVEF was normal (0.58 +/- 0.03). LV stroke volume index (SVI) was increased (48 +/- 3 ml/m2, P is less than 0.005), and RVSVI was normal (34 +/- 3 ml/m2). One patient had a markedly small RVEDV (45%). In group II, LVEDV and RVEDV were not different from normal (119 +/- 11% and 97 +/- 15%, respectively). LVEF was depressed (0.52 +/- 0.04, P is less than 0.001) and RVEF was normal (0.55 +/- 0.05). LVSVI was normal (38 +/- 5 ml/m2) and RVSVI was slightly decreased (29 +/- 4 ml/m2, P is less than 0.025). Two patients had a markedly small RVEDV (31%, 55%). EDV correlated with the pulmonary-to-systemic flow ratio (LV, r = 0.71; RV, r = 0.68). The data show that in most patients with AVC, LV and RV are enlarged in the uncomplicated form but not in the form with RV obstruction. LV function is more compromised than RV in both groups. RV hypoplasia is rare but was documented in both uncomplicated forms and forms with RV obstruction.
Total effective compliance, cardiac output and fluid volumes in essential hypertension.
Authors: London G M , Safar M E , Simon A C , Alexandre J M , Levenson J A , Weiss Y A
Published: June 2012

Total effective compliance, hemodynamic parameters, extracellular fluid volume, cardiopulmonary (CPBV) and total blood (TBV) volumes were determined in 32 men, including 14 normotensive controls and 18 sustained essential hypertensive patients. The effective compliance was calculated from the changes in central venous pressure recorded simultaneously with the changes in blood volume obtained after a rapid Dextran infusion. In normotensive controls, compliance was 2.08 +/- 0.09 ml/mm Hg/kg and was positively correlated with plasma (r = 0.79) and extracellular fluid (r = 0.84) volumes. In hypertensives, compliance was significantly reduced (1.49 +/- 0.06 ml/mm Hg/kg; P is less than 0.001) and was correlated negatively with the CPBV/TBV ratio (r = -0.75) and positively with the plasma volume/interstitial fluid volume ratio (r = 0.84). These results suggest that in normotensives, there is a regulatory mechanism between volume and compliance and that this contributes to maintaining filling pressure and cardiac output within normal ranges. In hypertensives, the reduced compliance could participate in the maintenance of normal values of cardiac output and extracellular fluid volume by influencing the partition of intravascular and extracellular fluid volumes.
Nonuniform cardiac sympathetic nerve discharge: mechanism for coronary occlusion and digitalis-induced arrhythmia.
Authors: Lathers C M , Kelliher G J , Roberts J , Beasley A B
Published: June 2012

This study examined nonuniform postganglionic cardiac sympathetic neural discharge as a possible mechanism involved in the production of coronary occlusion or ouabain-induced arrhythmias. After acute occlusion of the left anterior descending coronary artery in 12 cats, anesthetized with alpha-chloralose and pretreated with atropine, arrhythmia occurred within 3 min in eight animals; three of these died in ventricular fibrillation. In recordings from 15 nerves in the eight animals with arrhythmia, spontaneous discharge increased in nine nerves, decreased in five nerves, and showed no change in one nerve. This nonuniform neural discharge was associated with the development of arrhythmia after occlusion. In four of the cats, neural discharge did not change within the first 3 min after coronary artery occlusion and arrhythmia did not occur. Development of ouabain-induced arrhythmia was accompanied by a nonuniform pattern in the neural discharge (13 cats). This discharge may alter ventricular excitation and conduction to produce arrhythmia.
Coronary bypass graft fate: angiographic grading of 1400 consecutive grafts early after operation and of 1132 after one year.
Authors: FitzGibbon G M , Burton J R , Leach A J
Published: June 2012

All 1400 coronary bypass grafts, in 409 survivors of 414 patients undergoing 440 consecutive bypass operations, were selectively opacified in multiplane cineangiograms prior to hospital discharge and 1132 (81%) were restudied at one year. Grafts were graded A (excellent), B (fair) or O (occluded) by separate assessment of proximal and distal anastomoses and bypass trunks. In early graft studies 89% were patent (A and B), 79% graded A; at one year, 81% were patent, 74% graded A. Circumflex-marginal grafts fared less well early, but similarly late, compared with other grafts. Of all grafts graded B early, 37% became A, 39% remained B and 24% were occluded at one year; 90% of early graded A grafts remained so, 4% became B and 6% occluded; the grading system seems to have had useful predictive value. Distal anastomosis defects dictated early B grading in 81.3% of cases, trunk defects in 12.5% and proximal anastomosis defects in 2.7%. Trunk defects carried a worse prognosis for occlusion than did distal anastomosis defects. Side-to-side, vein-coronary anastomoses had a significantly higher patency rate than terminal end-to-side coronary anastomoses with the same veins.
Antiarrhythmic drug effect mimicked by spontaneous variability of ventricular ectopy.
Authors: Winkle R A
Published: June 2012

Twenty patients with frequent ventricular ectopic beats had a 5 1/2 hour ECG rhythm strip recorded. Individual patients showed a marked spontaneous variability from one half-hour to the next in the total number of ectopic beats (-99% to +1100%) and the occurrence of pairs or salvos. Although no patient received antiarrhythmic drugs, some patients showed a spontaneous change in arrhythmia which mimicked either drug suppression or drug-induced worsening of arrhythmias. If an antiarrhythmic drug had been given to these patients after the first half-hour, 65% would have been termed "drug responders," using the criteria of 50% reduction in ectopic beats and elimination of pairs or salvos during any half-hour period in the subsequent three hours. Spontaneous variability in ventricular ectopic beats causes serious problems when using ECG monitoring to evaluate antiarrhythmic drug response in individual patients. The arrhythmias averaged for the entire group remained stable during the recording period. Evaluating antiarrhythmic drugs by examining group response rather than individual patient response minimizes the effect of spontaneous variability.
Cardiac function in the normal newborn: additional information by computer analysis of the M-mode echocardiogram.
Authors: St John Sutton M G , Hagler D J , Tajik A J , Giuliani E R , Seward J B , Ritter D G , Ritman E L
Published: June 2012

Computer analysis of the M-mode echocardiogram in 50 normal newborns provided measurements of wall thicknesses and chamber size and, in addition, assessment of right and left ventricular wall, septal, and cavity dynamics throughout the cardiac cycle. Data obtained with this new technique indicated that (1) right and left ventricular cavity functions are similar in the normal newborn, (2) right and left ventricular cavity filling and emptying vary directly with peak rates of septal and ventricular wall thinning and thickening, respectively, and (3) there is a close time relationship among maximum left atrial dimension, minimum left ventricular dimension, and mitral valve opening. This analysis, which is the first complete analysis of the echocardiogram in the newborn, provides a normal range of septal and ventricular wall dynamics as well as right and left ventricular and left atrial function and has clinical implications in that it may allow early recognition of both congenital and perinatal myocardial disease.