bluuebunny/crossref_metadata_2025 huggingface dataset:
Certain Inevitable Relationships among the "Unipolar" Extremity Leads
Authors: LANGNER PAUL H. , BENJAMIN J. MALVERN , MOORE SAMUEL R.
Published: June 2012

It is demonstrated in this paper, both mathematically and experimentally, that the scalar sums of the three "unipolar" extremity leads when recorded with resistors of high value in the neutral network must equal zero if all the possible sources of error are eliminated. However, this fact has no bearing upon the validity of the Einthoven hypothesis or upon the theoretic concepts underlying the Wilson central terminal. In fact, when any three points are chosen at random to make a central terminal and the potential differences between each of the three points in turn and the central terminal are recorded, the scalar sum of these potential differences will invariably equal zero. It is also shown why any augmented "unipolar" extremity lead must be exactly 50 per cent greater than the respective unaugmented "unipolar" extremity lead if properly recorded.
The Water and Electrolyte Content of the Human Heart in Congestive Heart Failure with and without Digitalization
Authors: CLARKE NORMAN E. , MOSHER ROBERT E.
Published: June 2012

The hearts of 25 patients have been serially analyzed for water, chloride, sodium and potassium content. Sixteen hearts were of patients who died in circulatory heart failure; some received digitalis and some did not. The water content of all hearts was the same. In circulatory heart failure, the sodium increases and potassium decreases but the sum of the two remains the same as in normal hearts, indicating a reciprocal relationship. Digitalis in circulatory heart failure restores the alkali metal values and ratios of heart muscle to near normal levels. Digitalis exerts a direct chemical action on the heart muscle.
Assessment of Left Ventricular Stiffness in Primary Myocardial Disease and Coronary Artery Disease
Authors: MIRSKY ISRAEL , COHN PETER F. , LEVINE JAY A. , GORLIN RICHARD , HERMAN MICHAEL V. , KREULEN THOMAS H. , SONNENBLICK EDMUND H.
Published: June 2012

Stress-strain relations (σ-ε) were obtained in the form dσ/dε = kσ + c, where k is a stiffness constant. Utilizing the pressure-volume relation dP/dV = αP, the elastic stiffness (dσ/dε) and k were evaluated at end diastole in ten patients with normal ventricles (N), in 34 patients with coronary artery disease (CAD), and in 22 patients with primary myocardial disease. This latter group was classified into Type I (normal contraction patterns and elevated end-diastolic pressure), Type II (hypertrophy without obstruction), and Type III (hypokinetic and/or asynergic).

The mean values and standard error of the means (
sem
) of k and elastic stiffness were 14.8 ± 0.7, 329 ± 54 gm/cm
2
(N); 17.8 ± 0.3, 684 ± 80 gm/cm
2
(CAD); 18.2 ± 0.5, 1133 ± 127 gm/cm
2
(Type I); 22.4 ± 1.2, 833 ± 150 gm/cm
2
(Type II); 18.7 ± 0.6, 1623 ± 348 gm/cm
2
(Type III).

These studies indicate that 1) dP/dV, wall stress, and volume-mass ratio are the important determinants of stiffness, 2) normal stiffness levels can be recorded from hypertrophied ventricles, 3) CAD patients with end-diastolic pressure ≦ 12 mm Hg have normal stiffness levels, 4) normal contraction patterns and normal stiffness levels are not necessarily related.
The Variable Spectrum of Echocardiographic Manifestations of the Mitral Valve Prolapse Syndrome
Authors: DEMARIA ANTHONY N. , KING JAMES F. , BOGREN HUGO G. , LIES JAMES E. , MASON DEAN T.
Published: June 2012

The variety of echographic features associated with the mitral valve prolapse syndrome (MVPS) is not yet completely understood. Therefore, ultrasound recordings were obtained in 33 patients in whom mitral prolapse had been documented by biplane left ventricular cineangiography. Echographic abnormailities of the mitral leaflets during systole were recorded in 26/27 MVPS patients and 6/6 with ruptured chordae tendineae. In MVPS, the midsystolic mitral buckling, emphasized in early echocardiographic studies, was observed in only 12 patients. In our study, the most common aberrancy was abnormal pansystolic mitral motion in 14 patients, which in 12 was similar to the pansystolic bowing observed in all six patients with torn chordae. An additional echographic abnormality in MVPS was localized mitral collapse throughout systole in 10/14 patients with pansystolic prolapse; this finding was the most striking defect noted in five, in two of whom it was the only disturbance. Phonocardiography in MVPS showed typical midsystolic click and/or late systolic murmur in only 15/26 patients of whom ten had midsystolic mitral buckling. A variety of systolic clicks and/or murmurs occurred in the 14 patients with generalized bowing and/or localized collapse throughout systole on echocardiography. Thus, the mitral echographic spectrum of MVPS is comprised of three different abnormal patterns of systolic prolapse: buckling in midsystole, pansystolic bowing, and pansystolic collapse. These echocardiographic disorders commonly occur in the absence of classical auscultatory findings in MVPS and the most frequent abnormality on ultrasound is pansystolic bowing of both mitral leaflets.
Electrophysiologic Studies in Patients with Persistent Atrial Tachycardia
Authors: SCHEINMAN MELVIN M. , BASU DEBAL , HOLLENBERG MILTON
Published: June 2012

Clinical and electrophysiologic studies in two patients with chronic persistent atrial tachycardia unresponsive to drug or electroconversion therapy are reported. In both, exercise increased the atrial rate and decreased the atrioventricular nodal conduction time. The opposite effect occurred after β-adrenergic blockade. Single electrically-induced atrial depolarizations (A
2
) at progressively premature times resulted in a linear increase in the return cycle (A
2
A
3
) until plateau levels were achieved but failed to produce sinus rhythm. Abrupt cessation of continuous atrial pacing at rates up to 600 beats/min in one patient and up to 300 beats/min in the other resulted in a pause that was similar to the plateau levels of A
2
A
3
achieved during atrial scanning with single impulses. Our findings suggest that an ectopic atrial focus is responsible for this arrhythmia. The electrophysiologic properties of the ectopic pacemaker appear to be similar to the sinoatrial node in some respects but to differ in terms of spontaneous rate and in relative immunity from the effects of overdrive pacing.
Effect of Atrial Stimulation Site on the Electrophysiological Properties of the Atrioventricular Node in Man
Authors: BATSFORD WILLIAM P. , AKHTAR MASOOD , CARACTA ANTONIO R. , JOSEPHSON MARK E. , SEIDES STUART F. , DAMATO ANTHONY N.
Published: June 2012

The electrophysiological properties of the atrioventricular conduction system were compared in 16 patients using stimulation of the high right atrium (HRA) and a site within the coronary sinus (CS). The site of atrial stimulation significantly altered A-V nodal conduction time and refractoriness in eight patients (Group A) and did not change A-V nodal properties in the remaining patients. His-Purkinje conduction time and refractoriness were not affected by changing the atrial stimulation site. The atrial stimulation site may influence A-V nodal function by changing the site and/or mode of entry of the impulse into the A-V node.
Changes in Grafted and Nongrafted Coronary Arteries Following Saphenous Vein Bypass Grafting
Authors: MAURER B. J. , OBERMAN A. , HOLT J. H. , KOUCHOUKOS N. T. , JONES W. B. , RUSSELL R. O. , REEVES T. JOSEPH
Published: June 2012

Progression of disease in the native coronary arterial circulation was studied in 121 patients who underwent saphenous vein bypass graft surgery at the University of Alabama Medical Center, Birmingham, between 1969 and 1972, and who had a second coronary arteriogram at a mean interval of 11.7 months later. Two hundred thirteen arteries (10 triple, 74 double, 37 single) were grafted and 148 were not. Graft patency rate was 72%. Stenotic obstructive lesions in defined arterial segments and major branches were recorded for each artery at each examination. Pre and postoperative arteriograms were reviewed at the same time. Disease was expressed as "% stenosis" of each segment or branch examined. An arterial score, which was the sum of segments and branches seen on each occasion, was calculated for each artery and the scores were compared. New total occlusion, new obstructive lesions, and progression of pre-existing lesions were five times more frequent in grafted than in nongrafted arteries with comparable initial disease. New and progressive lesions were encountered with the same frequency in arteries with patent and occluded grafts. They occurred more frequently in segments proximal to the graft than in distal segments. Arteries with moderate (less than 75%) and arteries with severe (75-99%) stenosis had similar progression rates. Only 2% of segments of ungrafted arteries showed new total occlusions as compared to 60% of grafted arteries. The arterial score fell by 34% in grafted arteries and did not change in nongrafted arteries. These findings suggest that significantly fewer branches and segments of grafted arteries are seen following bypass grafting. New totally occlusive lesions are considerably more frequent in grafted than in nongrafted arteries and are not related to graft patency at one year after surgery. Disease progression in ungrafted vessels is relatively slow. These changes in the coronary arteries should be considered when assessing patients, particularly those with moderate degrees of stenosis, for bypass grafting.
Left Ventricular Size and Function and Heart Size in the Year Following Myocardial Infarction
Authors: FEILD BOLLING J. , RUSSELL RICHARD O. , MORASKI ROGER E. , SOTO BENIGNO , HOOD WILLIAM P. , BURDESHAW JOHN A. , SMITH MCKAMY , MAURER BRIAN J. , RACKLEY CHARLES E.
Published: June 2012

Interrelationships among left ventricular (LV) size, LV function, and heart size were investigated in 49 patients studied 2-12 months after myocardial infarction. LV end-diastolic volume (EDV) and ejection fraction (EF) were determined by biplane ventriculography. Heart size was estimated from chest films by the cardiothoracic ratio (CTR) and cardiac volume (CV) methods. Ventricular function (i.e., EF) was related to chamber size (i.e., EDV), but the correlation coefficient was not high (
r
= 0.74); thus, chamber size was not an accurate predictor of EF. Because of the close linear relation that exists between LV end-systolic volume and EDV (
r
= 0.98), a hyperbola describes the relation between EF and EDV. In general, EF was depressed (<0.50) when EDV exceeded 70 ml/m
2
, was <0.35 when EDV exceeded upper normal limits (110 ml/m
2
), and was <0.25 with chamber size >150 ml/m
2
. Thus relatively small chamber size (<150 ml/m
2
) was associated with a wide range in ventricular function, while large chamber size was associated with severe dysfunction (EF < 0.30). By either heart size method, cardiomegaly (CTR > 0.50 or CV > 540 ml/m
2
) was not found consistently until EDV exceeded 150 ml/m
2
. Hence normal heart size was often associated with moderate EF depression (0.49-0.30), while cardiomegaly was often associated with severe dysfunction. Clinical heart failure (CHF) was usually accompanied by EF < 0.30, but chamber size ranged from 101 to 331 ml/m
2
. Primarily because of this variation in chamber size, both normal heart size and cardiomegaly were at times associated with CHF.

The poor correlations of EF with CTR (
r
= –0.43) and CV (
r
= –0.52) preclude use of the heart size indices as accurate predictors of LV function. When the data were analyzed according to the presence or absence of cardiomegaly, the following generalizations could be made regardless of the heart size method used. Cardiomegaly was a reasonable indicator of postinfarction LV function, being associated with depressed function and often with CHF. However normal heart size was associated with either normal LV function, or commonly, with depressed function, often not clinically apparent.
The Treatment of Recurrent Ventricular Tachycardia with Bilateral Cervico-Thoracic Sympathetic-Ganglionectomy
Authors: LLOYD RICHARD , OKADA ROBERT , STAGG JAMES , ANDERSON ROBERT , HATTLER BRACK , MARCUS FRANK
Published: June 2012

Two patients had bilateral cervico-thoracic sympatho-ganglionectomy for treatment of disabling symptoms due to refractory ventricular tachycardia. In both patients treatment with antiarrhythmic drugs singly, in combination, or together with pacemaker overdrive had been ineffective in controlling this arrhythmia. Both patients had normal coronary arteriograms.

Bilateral thoracic sympathectomy appears to facilitate medical management of ventricular tachycardia in selected patients who are refractory to the usual medical treatment.
Differences in Distribution of Myocardial Abnormalities in Patients with Obstructive and Nonobstructive Asymmetric Septal Hypertrophy (ASH)
Authors: HENRY WALTER L. , CLARK CHESTER E. , ROBERTS WILLIAM C. , MORROW ANDREW G. , EPSTEIN STEPHEN E.
Published: June 2012

Patients with typical idiopathic hypertrophic subaortic stenosis (IHSS) represent only one subgroup of a cardiac disease in which the characteristic anatomic abnormality is asymmetric septal hypertrophy (ASH). In most patients with ASH, left ventricular outflow obstruction is absent and cardiac dysfunction presumably is due to widespread involvement of the left ventricle by an underlying myocardial abnormality. In other patients with ASH, left ventricular outflow obstruction is present (typical IHSS) and constitutes a major feature of the hemodynamic and physical findings. To determine whether patients with outflow obstruction also have the underlying myocardial abnormality diffusely involving the left ventricle, the gross morphology of hearts from patients with and without outflow obstruction were studied both by necropsy and by echocardiography. Echocardiographic studies revealed that the ventricular septum was thicker in obstructive ASH, a finding confirmed by the postmortem studies. The necropsy studies also indicated that although the left ventricular free wall was thickened in both obstructive and nonobstructive ASH, the configuration of the left ventricular free wall was distinctly different in the two groups. In obstructive ASH, the free wall was hypertrophied and identical in appearance to that seen in valvular aortic stenosis. Moreover, echocardiographic studies indicated that the thickening of the free wall behind posterior mitral leaflet appeared to regress after operative relief of the outflow obstruction. In contrast, the left ventricular free wall of severely symptomatic patients without outflow obstruction had a markedly different and unique appearance; the free wall of left ventricle directly behind the posterior mitral leaflet was of normal or less than normal thickness, whereas the remaining free wall was nonuniformly thickened. On the basis of these findings and the microscopic data presented in the companion paper, we conclude that the myocardial abnormality in obstructive ASH (typical IHSS) is localized largely to the ventricular septum, with left ventricular free wall thickening occurring as a consequence of outflow obstruction. In symptomatic patients with nonobstructive ASH, however, the data suggest that the left ventricle, including free wall, is extensively involved with a primary myocardial abnormality.
The Effects of Propranolol on Induction of A-V Nodal Reentrant Paroxysmal Tachycardia
Authors: WU DELON , DENES PABLO , DHINGRA RAMESH , KHAN ASHFAQUE , ROSEN KENNETH M.
Published: June 2012

Twelve patients with paroxysmal supraventricular tachycardia (PSVT) were studied before and after administration of 0.1 mg/kg i.v. propranolol. Echo zones for inducing atrioventricular (A-V) nodal reentry were determined using His bundle recording and the atrial extrastimulus technique. After propranolol the echo zone was abolished in two patients, decreased in one, unchanged in five, increased in two. In two patients echo zones appeared only after propranolol. Nine patients had episodes of sustained PSVT prior to propranolol. Following propranolol PSVT persisted in only five. In these five patients propranolol slowed the rate of PSVT.

The data were analyzed by plotting A
1
-A
2
and H
1
-H
2
interval curves. On the basis of these curves the patients were separated into those with "dual pathways" and those with "reflection." The effects of propranolol on both conduction patterns are discussed.

In summary, the actions of propranolol in PSVT patients were variable. Potentially beneficial effects included slowing of induced PSVT, loss of the ability to sustain PSVT, and decrease or total elimination of echo zones. Potentially deleterious effects included potentiation of the echo phenomenon with either increase or development of echo zones.
Determinants of Reversible Asynergy
Authors: BANKA VIDYA S. , BODENHEIMER MONTY M. , HELFANT RICHARD H.
Published: June 2012

To determine which factors may be of value in determining whether or not asynergic zones have residual contractile ability, the responsiveness of these zones to sublingual nitroglycerin (1/150 grs) was studied angiographically in 36 patients. The responsiveness of asynergy was correlated with the presence or absence of pathologic Q waves and coronary collaterals in the corresponding zones, as well as with anatomic location. Of the 25 asynergic segments which had corresponding pathologic Q waves, 11 (44.0%) responded to nitroglycerin while 14 (56%) remained unresponsive. In contrast, 30 (83.3%) of the 36 segments which did not have associated Q waves improved while only 6 (16.4%) did not (
P
< 0.005). Akinetic segments with Q waves were associated with a significant decrease in responsiveness (
P
< 0.02) compared to hypokinetic segments. Of the 26 segments with angiographically demonstrable collaterals, 22 (84.6%) improved and only 4 (15.4%) remained unchanged (
P
< 0.02). In contrast, of the 35 segments without collaterals, 19 (54.3%) were responsive and 16 (45.7%) did not respond. Seven (77.8%) of the 9 akinetic segments with collaterals exhibited improvement compared to only 5 (33%) of the 15 segments without collaterals (
P
< 0.05). In segments with pathologic Q waves, 70% of those associated with collaterals improved compared to only 27% without collaterals (
P
< 0.02). Relative to anatomic location, of 29 anterior wall segments, 24 (82.8%) responded compared to only 11 (45.8%) of 24 apical segments (
P
< 0.005). These data indicate that the presence of coronary collaterals and absence of pathologic Q waves in the corresponding zones are associated with a higher incidence of residual contractile ability of asynergic segments. Apical asynergy responds less frequently than asynergy in other anatomic zones.
Sudden Death as a Complication of Anomalous Left Coronary Origin From the Anterior Sinus of Valsalva
Authors: CHEITLIN MELVIN D. , DE CASTRO CARLOS M. , MCALLISTER HUGH A.
Published: June 2012

Both coronary arteries arising as a single or double vessel from the same sinus of Valsalva has been considered a minor congenital anomaly not affecting longevity. There are rare case reports in the literature of sudden death in young males with this anomaly of coronary origin. We have reviewed 51 such cases from the Armed Forces Institute of Pathology congenital heart disease accessions. There were 33 patients in whom both coronaries arose from the anterior sinus of Valsalva either as a single or double vessel and 18 in whom they arose from the left coronary sinus of Valsalva. Out of the 33 patients in whom the coronaries arose from the anterior sinus of Valsalva, 9 (27.3%) died sudden, unexplained deaths. There were no sudden unexplained deaths among the patients in whom both coronaries arose from the left sinus of Valsalva. It is evident that where the left coronary artery does not pass acutely posterior and leftward between the pulmonary artery and the aorta there is no risk of sudden death. All patients who died suddenly were male. The suggested mechanism for sudden death in these cases is that the acute leftward passage of the coronary artery along the aortic wall causes the entrance into the left coronary svstem to be slit-like. Under circumstances of increased cardiac activity with increased expansion of the pulmonary artery and aorta with exercise, there is stretching of the left coronary artery and a flap-like closure of the orifice of the left coronary with sudden, fatal myocardial ischemia.

We also present the first case where this anomaly was recognized in a 14-year-old boy and a surgical attempt was made to correct the problem by creating a non-collapsible funnel-like opening into the left coronary artery.
De Subitaneis Mortibus
Authors: JAMES THOMAS N.
Published: June 2012

In eight cases of scleroderma heart disease studied at necropsy special attention was paid to the cardiac conduction system and the coronary arteries. Six of the eight patients died suddenly, and all had some form of electrical instability of the heart. Distinct morphological abnormalities were present in the sinus node, atrioventricular (A-V) node and His bundle of every case, with sclerotic destruction of the sinus node being particularly striking in four of the hearts. Widespread lesions of the small coronary arteries (less than 1 mm diameter) were present in the ventricular myocardium, the sinus node artery and the A-V node artery. These lesions included mural and intimal fibrosis, endothelial proliferation, medial hyperplasia, fibrinoid necrosis and platelet-fibrin clots. The large coronary arteries were conspicuously normal or minimally diseased except in one case, and in that example there was no myocardial disease attributable to the single large coronary lesion found. It is concluded that arrhythmias and conduction disturbances are an integral component of the clinical picture of scleroderma heart disease, that this is associated with structural abnormalities in the centers of impulse formation and conduction, and that widespread narrowing lesions of the small coronary arteries (but not the major trunks) are important as a basis for fibrotic and degenerative changes throughout the heart. Some components of the fibrosis, particularly in the sinus node, seem disproportionate and suggest that both microvascular and primary collagen abnormalities contribute to the pathogenesis of scleroderma heart disease.
Characteristics of Hypertension in the Black Population
Authors: KILCOYNE MARGARET M. , THOMSON GERALD E. , BRANCHE GEORGE , WILLIAMS MICHAEL , GARNIER CHARLES , CHILES BENNY , SOLAND TOVE
Published: June 2012

The renin-angiotensin system was examined in 146 black patients with essential hypertension. Classification into three categories was made according to plasma renin activity as measured by the radioimmunoassay of Angiotensin I and the accompanying sodium excretion. Differences among patients in the three renin groups (low, normal, and high) were not observed with respect to the incidence of cerebrovascular and cardiovascular events. No other discriminating variables could be identified by multivariate discriminant analysis. Low renin patients were distinguished in having a reduced sodium excretion compared to normal and high renin patients. Although total exchangeable sodium was not measured in this group of patients, other investigators have reported a higher exchangeable sodium in low renin patients than in those with normal or high values. This possibility, together with recent evidence in experimental models of low renin hypertension, that the affinity of angiotensin for its vascular receptors may be sodium dependent suggests that the incidence of vascular events may relate more specifically to angiotensin-vascular receptor interaction than to measurements of circulating renin.
Effect of Nitroprusside on Left Ventricular Dynamics in Mitral Regurgitation
Authors: GOODMAN DANIEL J. , ROSSEN RONALD M. , HOLLOWAY EARL L. , ALDERMAN EDWIN L. , HARRISON DONALD C.
Published: June 2012

In order to evaluate the circulatory action of vasodilator therapy in patients with significant mitral regurgitation, sodium nitroprusside was infused intravenously in 14 patients who had mitral regurgitation due to a variety of causes. In 13 of these patients, valvular insufficiency had been present for several years. The mean arterial pressure fall from 88 ± 1.2 to 71 ± 2.1 mm Hg was accompanied by a significant decrease in pulmonary artery pressure (from 27.4 ± 2.7 to 19.1 ± 2.4 mm Hg), pulmonary artery wedge v wave (from 31.7 ± 3.3 to 17.0 ± 1.9 mm Hg), and left ventricular end-diastolic pressure (from 16.7 ± 1.6 to 9.3 ± 1.2 mm Hg). In 10 patients significant decreases in angiographic end-diastolic volumes (from 196 ± 10 to 177 ± 10 ml) and end-systolic volumes (from 90 ± 10 to 77 ± 9 ml) were accompanied by slight decreases in the total stroke volume and slight increases in the ejection fraction. The improved forward stroke volume index (from 27 ± 3.0 to 33 ± 2.1 ml) was due to a very significant reduction in the regurgitant fraction (from 57 ± 6 to 42 ± 6%). Nitroprusside, therefore, has beneficial hemodynamic effects in patients with chronic mitral regurgitation.
Atherosclerosis Complicating Chronic Hypertension
Authors: DUSTAN HARRIET P.
Published: June 2012

The accelerating effect of hypertension on atherogenesis in the aorta and iliofemoral and coronary arteries is presented here as a graded function of elevated intraarterial pressure. Predilection of the abdominal aorta and iliofemoral arteries for atherosclerosis can be explained on the basis of pressure augmentation by reflected pressure pulse waves and the increase in hydrostatic pressure that is produced by standing. Wave reflection is intensified by vasoconstriction, which is a characteristic not only of hypertension but also occurs with upright posture. Standing also raises the hydrostatic pressure of blood in vessels below heart level. Coronary atherosclerosis seems likely to relate to the fact that the coronary vessels are located in an area of high pressure in the arterial system and that their intramyocardial branches are normally completely occluded during systole — a condition which could be accompanied by subtle differences in the pressure-volume characteristics of the epicardial vessels.

Evidence is presented from actuarial statistics, epidemiologic studies, and laboratory experiments to indicate that the level of arterial pressure has a measurable effect on the metabolism of arterial smooth muscle cells. Thus arterial pressure is viewed as having a metabolic determinant role in addition to its vital role in the circulation of blood.
The Relationship Between Sinoatrial Conduction Time and Sinus Cycle Length During Spontaneous Sinus Arrhythmia in Adults
Authors: REIFFEL JAMES A. , BIGGER J. THOMAS , KONSTAM MARVIN A.
Published: June 2012

It is well known that atrioventricular conduction varies as a function of atrial rate. However, rate related changes in sinoatrial conduction time (SACT) have not been examined. To determine the relationship between SACT and sinoatrial cycle length (SCL) in man, atrial and His bundle electrograms were recorded during atrial premature stimulation in each of nineteen patients with sinus arrhythmia. Ten of nineteen had asymptomatic, intermittent sinus bradycardia; 3/19 had persistent sinus bradycardia with nonspecific symptoms; 6/19 were felt to represent the sick sinus syndrome. In 18/19 individuals, there was a clearcut, inverse, linear relationship between SACT and SCL, i.e., as SCL increased, SACT decreased. Although this resembles the increase in PR interval that occurs with a decrease in atrial cycle length during atrial pacing, it contrasts sharply with the unchanged or increased PR interval that accompanies spontaneous increases in SCL. Although the range of patients' SACTs at any given SCL was large, the slope of ΔSACT/ΔSCL was remarkably similar in most patients and was quite steep. One patient had episodes of 2:1 S-A block. As predicted, these occurred only at her shortest SCLs. Possible explanations for this behavior are considered and the clinical relevance of these observations is discussed.
Myocardial Necrosis from Direct Current Countershock
Authors: DAHL CHARLES F. , EWY GORDON A. , WARNER E. D. , THOMAS EVAN D.
Published: June 2012

The effect of varying both paddle electrode size and the time interval between direct current countershock on myocardial necrosis was studied. Forty-two dogs were divided into seven groups of six dogs each. All dogs were given ten consecutive, 240 watt-second countershocks (delivered energy into a 50 ohm load). Three groups were shocked with paddle electrode diameters of 8.0 cm (standard electrodes), two groups with paddle electrode diameters of 12.8 cm (large electrodes), and two groups with paddle electrode diameters of 4.3 cm (small electrodes). The time intervals between discharges in the groups shocked with the standard electrodes were 15 seconds, one minute, and three minutes. The time interval between discharges in the groups shocked with small and large electrodes was 15 seconds and three minutes. Myocardial necrosis was quantitated by precordial electrocardiographic mapping recorded minutes after, and by gross and microscopic examination of the hearts four days after direct current countershock.

When the time interval between discharges was shorter, myocardial necrosis was greater. When the time interval between discharges was constant, more necrosis was produced with smaller-sized paddle electrodes. It is concluded that large paddle electrodes should be used for delivering direct current countershocks, and that during elective cardioversion, consecutive discharges should be delivered at time intervals greater than three minutes.
Sinus Node Re-entry
Authors: NARULA ONKAR S.
Published: June 2012

Data in 20 patients with normal sinus rhythm who, following induced premature atrial beats (PABs), manifested re-entry in the region of the sinus node are presented. PABs at coupling intervals ranging between 230-535 msec were followed by sinus node re-entry (SNR). Several criteria were applied to diagnose SNR: the temporal sequence of atrial excitation, the intra-atrial conduction time, the shape and polarity of the P waves, and manifestation of re-entry independent of atrioventricular (A-V) nodal delays. In 18 patients SNR lasting for one to several beats was observed. In the remaining two patients sustained SNR was manifested as supraventricular tachycardia (SVT), with cycle lengths ranging between 320-500 msec, which persisted for several minutes prior to its termination by properly timed atrial stimuli. In one of the latter two patients sustained SNR and SVT were produced only after atropine administration. Sinus node re-entry could be elicited at will in a specific echo zone with a duration ranging between 10-170 msec. In some cases SNR was also observed during and on cessation of regular atrial pacing. The latter observation provides a possible explanation for the unexpected sinus node acceleration seen sometimes on termination of atrial pacing. It is demonstrated that SNR for a single beat may fallaciously simulate sinus node entrance block. Simultaneous occurrence of re-entry at multiple sites, i.e., the sinus node and the A-V node, with resultant fusion P waves is also demonstrated. This study provides another mechanism for the genesis of regular and irregular SVT. The analysis and localization of the re-entry circuit may prove to be of clinical and therapeutic significance in selected patients.
Maximum Treadmill Exercise Electrocardiography in Female Patients
Authors: LINHART JOSEPH W. , LAWS JAMES G. , SATINSKY JONATHAN D.
Published: June 2012

Exercise testing has become standardized for the diagnostic and functional evaluation of male patients but little data is available regarding its specificity and sensitivity in the female. Therefore, maximum treadmill exercise (Bruce protocol) was performed on 98 consecutive females and compared to coronary arteriography. Using 50% obstruction as indicating coronary artery disease and 1 mm ST-segment depression (horizontal or downsloping) as positive for ischemia, 24 patients had coronary artery disease with seven false-negative results (sensitivity = 71%) and 74 patients had no coronary artery disease with 16 false-positive responses (specificity = 78%).

Five of seven false-negative tests were in patients with single-vessel disease. Eleven of 16 false-positive responses were in patients on digitalis, diazepam, or methyldopa. In 39 patients on no drug therapy except for nitroglycerin there were no false negatives and only four false-positive tests. There were no false negatives and only two false-positive tests in 34 patients with normal resting electrocardiograms. Only one of 18 patients with both normal resting electrocardiograms and on no drug therapy had a false-positive test result. Eleven false-positive and seven false-negative results occurred in 40 patients with both an abnormal resting electrocardiogram and associated drug therapy.

The exercise electrocardiographic response in female patients is similar to the male when patients with resting electrocardiographic abnormalities and concomitant drug therapy are eliminated.
Hemodynamic Predictors of Myocardial Oxygen Consumption During Static and Dynamic Exercise
Authors: NELSON RICHARD R. , GOBEL FREDARICK L. , JORGENSEN CHARLES R. , WANG KYUHYUN , WANG YANG , TAYLOR HENRY L.
Published: June 2012

Hemodynamic predictors of myocardial oxygen consumption (MVO
2
) during static and dynamic exercise were examined in ten normal subjects. Studies were done under the following circumstances: 1) during upright bicycle exercise at an average heart rate of 147 beats/min, 2) during static exercise with an isometric load in the left hand equal to 17% of the maximal voluntary contraction (MVC), and 3) during combined dynamic exercise (average heart rate 147 beats/min) and static exercise using 17% MVC of the left hand. Mean myocardial blood flow (MBF) was 181 ml/100 gm LV/min during dynamic exercise, 98 ml/100 gm LV/min during static exercise, and 201 ml/100 gm LV/min during combined static and dynamic exercise. Addition of a static load to the dynamic load resulted in a higher blood pressure (average 12 mm Hg), MVO
2
and MBF than during dynamic exercise alone. MVO
2
correlated best with products of heart rate and blood pressure regardless of whether the blood pressure was obtained by a central aortic catheter (
r
= 0.88) or by a blood pressure cuff (
r
= 0.85).

When the current data were combined with previous data, 82 determinations of MVO
2
and MBF in 29 normal subjects during several levels of upright exercise were available for analysis. Forty-four determinations were done during dynamic upright exercise, 18 during exercise after propranolol, ten during combined static and dynamic work, and ten during static work alone. MVO
2
correlated best with the product of heart rate and blood pressure (
r
= 0.86). Heart rate alone correlated better with MVO
2
(
r
= 0.82) than did the tension time index (
r
= 0.65) or the product of systolic blood pressure, heart rate, and ejection time (
r
= 0.68). The readily measured variables of heart rate and of heart rate x blood pressure correlated well with MVO
2
in normal young men during exercise under a wide variety of circumstances.
Indices Predicting Long-term Survival after Valve Replacement in Patients with Aortic Regurgitation and Patients with Aortic Stenosis
Authors: HIRSHFELD JOHN W. , EPSTEIN STEPHEN E. , ROBERTS ARTHUR J. , GLANCY D. LUKE , MORROW ANDREW G.
Published: June 2012

The long-term results of aortic valve replacement were reviewed in all 88 patients with isolated aortic regurgitation and all 103 patients with isolated aortic stenosis who were operated upon at the National Heart and Lung Institute from 1963 to 1971. Survival curves were compared to determine whether any of 30 preoperative clinical and hemodynamic findings correlated with long-term survival. The indices that were of predictive value in patients with aortic regurgitation were found to be different from those in aortic stenosis. Symptoms, cardiac index, and cardiothoracic ratio did not influence survival in patients with aortic regurgitation. In these patients, survival was inversely correlated with the level of left ventricular end-diastolic pressure (LVEDP): six-year survival was 74% in patients with LVEDP ≤ 10 mm Hg, 41% with LVEDP 11-20 (
P
< .05), and 30% with LVEDP > 20 (
P
< .01). Survival also was lower in patients with aortic regurgitation who had elevated pulmonary arterial and left atrial pressures, and in patients with electrocardiographic evidence of severe left ventricular hypertrophy (LVH). Using an LVH point score method (Romhilt-Estes), 56% of patients with a score ≤ 6 survived six years; 29% with a score > 6 survived (
P
< .02). Survival in aortic stenosis did not relate to any of the above, but did correlate with preoperative functional class. Five-year survival was 70% in class II, but only 40% in class III-IV (
P
< .02). Moreover, cardiothoracic ratio in patients with aortic stenosis correlated with survival in an unexpected way. Eleven of 31 patients with cardiothoracic ratio ≤ .45 had sudden unexplained death postoperatively, compared to only six of 72 patients with cardiothoracic ratio > .45 (
P
< .01). This difference did not correlate with postoperative hemodynamic measurements, including magnitude of the transprosthetic gradient. We conclude that certain preoperative indices are of value in predicting long-term prognosis after valve replacement for aortic regurgitation and for aortic stenosis, but that the specific predictive indices for the two groups differ.
Systolic time intervals by echocardiography.
Authors: Stefadouros M A , Witham A C
Published: June 2012

Technical difficulties in recording phonocardiogram or indirect carotid pulse occasionally preclude determination of the systolic time intervals. Accordingly, an alternative method was tested in 52 patients, using high-speed strip chart recording of the aortic valve echocardiogram. Satisfactory records were obtained in 36. The interval from opening to closing of the aortic valve (ejection time) was subtracted from the interval between the Q wave of the electrocardiogram and the closing of the aortic valve (total electromechanical systole) to provide the pre-ejection period. When these intervals and the pre-ejection period/ejection time ratio were compared to corresponding values obtained by conventional methods from the simultaneously recorded phonocardiograms and indirect carotid pulses, a high degree of correlation (r greater than 0.97) was found. Differences between the two methods for each interval were insignificant, being greatest in the case of the ejection time but never exceeding 16 msec. These findings indicate that the echocardiogram of the aortic valve provides an alternative, noninvasive method for determination of the systolic time intervals whenever the usual methods fail.
Myocardial blood flow response to isometric (handgrip) and treadmill exercise in coronary artery disease.
Authors: Lowe D K , Rothbaum D A , McHenry P L , Corya B C , Knoebel S B
Published: June 2012

Thirty patients undergoing coronary cineangiography for diagnosis or evaluation of coronary artery disease had myocardial blood flow studies pre and post handgrip (isometric) exercise just prior to cineangiography. The handgrip was maintained at one-third maximum effort for three minutes. The patients also had treadmill exercise testing a day or two prior to the study. Treadmill testing was carried out until angina or positive ST-segment changes occurred or the patient attained 90% of predicted maximal heart rate. Of the 30 patients, seven had no coronary artery disease and 23 had significant disease, i.e., greater than 75% occlusion of at least one major coronary artery. Six of the 23 patients (26%) with disease had angina with handgrip and demonstrated a decreased myocardial blood flow, a significantly different response from the patients without agina (P less than 0.001). For the group without angina, the blood flow response was not significantly different from the normal group. Treadmill tests were positive in 19 of the 23 patients with coronary disease (83%). The arterial systolic and diastolic pressure rise was almost identical with the two stresses. The heart rate response, however, was significantly different (P less than 0.001), the rate increase being greater with treadmill exercise. The myocardial blood flow data demonstrate the relative insensitivity of handgrip exercise for the diagnosis of coronary artery disease. In terms of the supply demand ratio (diastolic pressure time/systolic pressure time) concept for subendocardial perfusion, it is possible that the difference between handgrip and treadmill stress may be due to the different heart rate response, more rapid heart rates having a relatively greater effect on diastolic than on systolic time indices, all other factors being equal.
Prognosis in coronary artery disease. Angiographic, hemodynamic, and clinical factors.
Authors: Burggraf G W , Parker J O
Published: June 2012

Evaluation of the results of surgery for coronary artery disease requires a knowledge of the clinical course of patients not having this mode of treatment. To obtain such information we performed a retrospective analysis of the fate of 266 patients with arteriographically documented significant stenosis following from one to ten years. For the entire group the five year survival was 73%. Subdivided into single, double or triple vessel disease categories the percent five year survival rates were respectively 92, 65 and 55. A history of angina pectoris or myocardial infarction prior to angiography did not affect survival. However, hypertension, congestive heart failure, abnormal hemodynamics or left ventricular asynergy were all associated with a diminished five year survival, the values being respectively 61%, 38%, 62% and 58%. These results should be of VALUE IN ASSESSING THE PROGNOSIS OF NONSURGICALLY TREATED PATIENTS WITH CORONARY ARTERY DISEASE.
Mechanism of normal splitting of the second heart sound.
Authors: Curtiss E I , Matthews R G , Shaver J A
Published: June 2012

The mode of inspiratory augmentation (1A) of the A2-P2 interval was investigated in seven normal volunteers (group 1) and six patients with pulmonary hypertension of diverse etiology (group 2) using catheter-tip micromanometers. In group 1 subjects, inspiratory widening of this interval was found to average 27.2 msec, of which 7.6 plus or minus 2.7 msec (1 sd) or 27 plus or minus 7% was due to a decrease in the Q-A2 interval. The major contribution of Q-P2 interval prolongation was divided into two components: a) Q-O was measured from the onset of the QRS to the onset of the rapid descent of the right ventricular (RV) negative dp/dt, which was felt to reflect the duration of RV electromechanical systole, b) O-P2 or Q-P2 - Q-O. Increase in the Q-O interval accounted for only 7.7 plus or minus 5.0 msec or 28 plus or minus 12% of the total IA. The major single component of IA was the increase in O-P2 which averaged 11.9 plus or minus 3.0 msec. Five of six group 2 patients demonstrated significant respiratory change in Q-P2 intervals. In contrast to group 1 subjects, however, this was accomplished primarily via increases in the duration of RV electromechanical systole. The O-P2 interval is felt to primarily reflect the impedance characteristics of the pulmonary vascular bed. It is concluded that physiologic splitting of the second heart sound in normal subjects is most probably due to an inspiratory decrease in impedance of the pulmonary bed rather than the traditional explanation of prolongation of RV systole secondary to an increase in venous return. When the normal impedance characteristics of this bed are lost, as in pulmonary hypertension, IA must occur primarily via increases in the duration of RV systole. The inspiratory delay from the conclusion of RV systole to the occurrence of P2 is attributed to the inertiance of the RV stroke mass.
Visualization and measurement of the main bronchi by tomography as an objective indicator of thoracic situs in congenital heart disease.
Authors: Partridge J B , Scott O , Deverall P B , Macartney F J
Published: June 2012

When investigating complex congenital heart disease, determination of atrial situs is essential. Pathological studies have demonstrated that the best predictor of atrial situs is thoracic situs. To assess thoracic situs, bronchial tomography was performed in 92 patients with congenital heart disease. Sixty-four of these, without abnormalities of situs or cardiac position, formed 'normal' controls. The lengths of the left and right main bronchi were measured. When these were related to age, and the results analyzed statistically, linear discriminant equations resulted giving a chance of only 0.09% of misclassifying a bronchus of unknown morphology. The lowest ratio between bronchial lengths (BLR) in any individual was 1.71:1. These results were then used to assess thoracic situs in 17 patients with abnormal situs or CARDIAC POSITION. In 7 (2 with situs inversus), abdominal and thoracic situs agreed. Of 6 patients with bilateral left lung, 3 had an interrupted inferior vena cava. Of 4 patients with presumptive asplenia, 2 had bilateral right lung, but two had thoracic lateralization, one solitus and one inversus. The highest BLR in thoracic isomerism was 1.4:1. This emphasizes the complex interrelation of splenic status, thoracic, and abdominal situs, but demonstrates the value of bronchial measurement particularly in apparent situs indeterminatus.
Demonstration of sustained sinus and atrial re-entry as a mechanism of paroxysmal supraventricular tachycardia.
Authors: Wu D , Amat-y-leon F , Denes P , Dhingra R C , Pietras R J , Rosen K M
Published: June 2012

Electrophysiological studies in five patients with documented (4) or suspected (1) paroxysmal supraventricular tachycardia (PSVT), suggested sinus or atrial reentrance (SR or AR). Two of the patients had preexcitation, three had evidence of atrial enlargement, and all had organic heart disease. The following observations supported a diagnosis of SR and AR; 1) induction of sustained PSVT with atrial extrastimulus technique allowing definition of an echo zone; 2) induction of sustained PSVT during constant rapid atrial pacing at a rate less than that producing A-V nodal Wenckebach periods, or producing normalization of QRS complex in patients with pre-excitation: 3) P waves preceding each QRS during PSVT with an A-H interval appropriate for the rate of the PSVT; 4) antegrade P wave morphology during PSVT, a normal high to low sequence of right atrial activation (SR), or P wave morphology and atrial activation sequence different from sinus (AR); 5) lack of correlation of PSVT induction with critical A-H interval. The rates of induced sustained PSVT ranged from 114 to 143 beats/min, and were similar to those observed during spontaneous episodes of PSVT in the four patients. PSVT could be terminated with critically timed extra-stimuli or carotid massage. In conclusion, SR and AR appear to be mechanisms of spontaneous PSVT in man. Rates of SR and AR PSVT tend to be relatively slow.