bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of a reentry circuit in the common type of atrial flutter in man.
Authors: Disertori M , Inama G , Vergara G , Guarnerio M , Del Favero A , Furlanello F
Published: June 2011

To investigate the mechanism of atrial flutter (AF) in humans, we studied 13 patients during episodes of spontaneous common AF, with simultaneous multiple atrial endocavitary recordings and atrial programmed stimulation. In all patients, low paraseptal atrial activation preceded high right atrial activation, and the latter preceded mid- or low lateral right atrial activation (recorded in five patients). Programmed atrial stimulation resulted in early reset of the AF cycle, with an unchanged poststimulation AF activation pattern. The poststimulation cycle recorded from an even potential to the site of stimulation was always shorter than the basic flutter cycle length. The poststimulation cycle recorded at the site of stimulation was always equal to or longer than the flutter cycle length. These results strongly favor the existence of a reentry circuit to which the extrastimulus has access.
Persistent improvement after coronary bypass surgery: ergometric and angiographic correlations at 5 years.
Authors: Frick M H , Harjola P T , Valle M
Published: June 2011

One hundred patients with angina pectoris who fulfilled specific entry criteria were randomly assigned to either medical therapy or bypass surgery. These groups were subjected to annual exercise testing during a 5-year follow-up period. The degree of revascularization was assessed by graft and native vessel angiography at 3 weeks, 1 year and 5 years after the operation. The exercise tolerance of the medical group remained largely unchanged during the follow-up. Eighty-five to 95% of the patients were using beta-blocking compounds at the successive testing situations. The surgical group exhibited a sustained improvement in exercise tolerance: Total work increased by 39-66% (p less than 0.02-0.001) and maximal ergometric load by 23-35% (p less than 0.01-0.001), and maximal ST depression decreased by 39-61% (p less than 0.05-0.001). The use of beta-blocking compounds in the surgical group steadily increased, from 44% at 6 months after operation to 63% of patients at 5 years. Division of the surgical group into subsets of complete and incomplete revascularization revealed that the improvement was confined to complete revascularization. Thus, the improved exercise tolerance after bypass surgery was a result of successful reestablishment of effective coronary perfusion; despite graft attrition (15% in 5 years) and new lesions in the native arteries, this improvement persisted for 5 years with appropriate medical therapy.
Habitual physical activity and high-density lipoprotein cholesterol in men with primary hypercholesterolemia. The Lipid Research Clinics Coronary Primary Prevention Trial.
Authors: Gordon D J , Witztum J L , Hunninghake D , Gates S , Glueck C J
Published: June 2011

The association of habitual physical activity with plasma high-density lipoprotein (HDL) cholesterol and total triglyceride (TG) was examined in 7106 asymptomatic 35-59-year-old white men with primary type II hyperlipoproteinemia who attended the second screening visit of the Lipid Research Clinics Coronary Primary Prevention Trial. Subjects were rated by usual level of physical activity at work and outside of work and the frequency of strenuous physical labor or exercise. By each of these three criteria, physical activity was monotonically related to HDL cholesterol and TG: the most physically active men had the highest HDL cholesterol and lowest TG levels. With respect to physical activity outside of work, for example, mean HDL cholesterol and TG were 46.4 and 152.1 mg/dl, respectively, in the most active group, and 41.4 and 186.7 mg/dl in the most sedentary group. Physical activity remained significantly predictive of HDL cholesterol and TG when other known correlates of these plasma constituents--age, Quetelet index, plasma total cholesterol, cigarette smoking, alcohol intake, and clinic--were controlled individually by two-way analyses of variance or jointly by analysis of covariance. The association of physical activity with very low density lipoprotein cholesterol was parallel to but weaker than its association with TG. Low-density lipoprotein and total cholesterol were not significantly related to physical activity.
Intravenous short-term infusion of streptokinase in acute myocardial infarction.
Authors: Schröder R , Biamino G , von Leitner E R , Linderer T , Brüggemann T , Heitz J , Vöhringer H F , Wegscheider K
Published: June 2011

Short-term i.v. infusion of streptokinase was performed in 93 patients within 6 hours after the onset of acute myocardial infarction. Twenty-six patients underwent angiography in the acute phase (group A) and 52 underwent angiography in the fourth week only (group B); 15 patients had no angiography. Seven patients died during the hospital stay and six suffered nonfatal reinfarctions. There were no bleeding complications. In 11 of 21 group A patients, occluded coronary arteries were opened within 1 hour after the streptokinase infusion was started. In 84% of groups A and B, the infarct-related coronary artery was patent in the fourth week. In 75% of the patent arteries, the residual luminal diameter stenosis was less than 70%. According to serial serum CK-MB curves, recanalization was achieved mostly within 1-2 hours. Myocardial salvage was indicated by improvement in local contraction disorders in the recanalized group A patients and by the significant relationship between infarct size and time from symptom onset to treatment in group B. These data suggest that a high-dose, short-term, i.v. infusion of streptokinase is a safe and efficient method of restoring coronary blood flow. Expeditious initiation of i.v. streptokinase infusion is a critical determinant for early recanalization and salvage of myocardium. Patients with thrombotically subtotal occlusion probably receive the most benefit. Evaluation of the true impact on survival and myocardial function will require controlled clinical trials.
Extent of atrial participation in atrioventricular-reciprocating tachycardia.
Authors: Morady F , Wang Y S , Scheinman M M , Sung R J , Shen E , Shapiro W A
Published: June 2011

Twenty-one patients with atrioventricular (AV) bypass tracts underwent electrophysiologic studies. The bypass tract was left-sided in 15 patients, septal in five and right-sided in one patient. Orthodromic AV-reciprocating tachycardia was induced in all 21 patients, with a mean tachycardia cycle length of 342 +/- 59 msec. The introduction of single stimuli in the high right atrium during tachycardia resulted in simultaneous dissociation of the high right atrial and low septal atrial electrograms in nine patients. In six patients, high right atrial overdrive pacing during tachycardia resulted in simultaneous dissociation of the high right atrial and low septal atrial electrograms for two to five consecutive beats. All patients in whom the low septal atrial electrogram was dissociated from the tachycardia had a left-sided bypass tract. In no patient was the coronary sinus atrial electrogram dissociated from the tachycardia by high right atrial pacing. Dissociation of the low septal atrial electrogram (as recorded in the His bundle electrogram) from AV-reciprocating tachycardia suggests that the portion of the right atrium adjacent to the AV node may not be a necessary link in the tachycardia circuit. This observation suggests that the site of entry of left-sided impulses into the AV node may be different from that of right-sided impulses.
Comparison of total body surface map depolarization patterns of left bundle branch block and normal axis with left bundle branch block and left-axis deviation.
Authors: Sohi G S , Flowers N C , Horan L G , Sridharan M R , Johnson J C
Published: June 2011

Total body surface maps from 15 subjects with left bundle branch block and normal axis (LBBB-NA) and 10 subjects with left bundle branch block and left axis (LBBB-LA) were analyzed and compared with maps from normal subjects. In 19 of the 25 subjects with LBBB, the timing of early upper sternal positivity was similar to that of normal subjects, indicative of timely but oppositely directed septal activation. The right ventricular breakthrough was normally located in all, but was earlier after the onset of QRS than expected in some. The initial portion of the positivity produced by left ventricular activation was located in the upper anterior chest in both LBBB-NA and LBBB-LA, but its onset was generally delayed compared with that in normal subjects, presumably because of the time taken by the right-to-left septal activation. Also, the total duration of this positivity was longer than in normal subjects and extended considerably beyond 90 msec, indicating prolonged activation of the anterior free wall of the left ventricle. In LBBB-NA, this upper anterior positivity remained anterior throughout depolarization, but in LBBB-LA it moved toward the left shoulder and the left upper back, presumably due to the posterior orientation of the terminal portion of depolarization. This terminal orientation in patients with LBBB-LA was thought to be due to the additional delay in the activation of the anterobasal portion of the left ventricle caused by selective involvement of the left anterior fascicle.
Bundle branch reentry: a possible mechanism of ventricular tachycardia.
Authors: Touboul P , Kirkorian G , Atallah G , Moleur P
Published: June 2011

Electrophysiologic studies were performed in three patients suffering from attacks of paroxysmal tachycardia with wide QRS complexes. Two patients had atrioventricular dissociation. The arrhythmia could be initiated and terminated by premature ventricular stimulation in all three patients. One patient developed the arrhythmia after rapid atrial stimulation. In each subject, the QRS complexes during tachycardia were identical to recorded supraventricular beats (left bundle branch block pattern in two cases and right bundle branch block pattern in one). A His bundle potential was noted before the QRS complex; the HV interval was equal to or longer than that of the sinus beats. The following observations suggested the presence of a bundle branch reentry mechanism: (1) the relationship between bundle branch block development and tachycardia initiation; (2) the occurrence of tachycardia after electrically induced His-Purkinje reentry; (3) the ability of premature ventricular stimulation during tachycardia to advance the timing of the His deflection and QRS complex, with an unchanged or slightly increased HV interval; and (4) the termination of arrhythmia by premature ventricular depolarization blocked within the bundle branch system. Our results support the idea that bundle branch reentry can play a role in the genesis of ventricular tachycardia.
Antegrade slow bypass conduction after closed-chest ablation of the His bundle in permanent junctional reciprocating tachycardia.
Authors: Critelli G , Perticone F , Coltorti F , Monda V , Gallagher J J
Published: June 2011

A case of permanent junctional reciprocating tachycardia in a 36-year-old woman successfully treated with closed-chest interruption of the His bundle is reported. Tachycardia had lasted for 14 years and showed a retrograde P wave (P') and RP' longer than PR' interval. The tachycardia used an anomalous pathway with a long conduction time in the retrograde direction. The atrial end of the anomalous pathway was located near the coronary sinus orifice. His ablation was accomplished by delivering a direct-current shock from a cardioversion unit to the nodal-His zone by means of a conventional electrode catheter percutaneously introduced via the femoral vein. Two shocks were necessary to obtain the desired results. After the procedure, complete atrioventricular block below the His bundle was induced, while antegrade conduction was assured through the anomalous pathway that showed decremental properties. During 7 months of follow-up, stable sinus rhythm with a long PR interval has been observed; the patient has remained free from tachycardia. Furthermore, she is not pacemaker-dependent and requires no cardioactive medication. This case demonstrates the therapeutic value of closed-chest ablation of the His bundle in a patient with permanent junctional reciprocating tachycardia, as well as demonstrating for the first time that the underlying accessory pathway is capable, in some instances, of antegrade conduction.
Coronary anatomy and prognosis after myocardial infarction in patients 60 years of age and younger.
Authors: Roubin G S , Harris P J , Bernstein L , Kelly D T
Published: June 2011

Two hundred twenty-nine hospital survivors of acute myocardial infarction (MI) age 60 years or younger underwent coronary arteriography a median of 2 weeks after infarction and were followed a median of 24 months (range 6-62 months). For 62%, MI was the first presentation of coronary disease and 75% were in clinical Killip class I. Overall outcome was good: 96% survival at 1 year and 95% survival at 2 years. This was due to the high prevalence of patients with one-vessel disease (58%), with a survival of 99% at 1 year and 96% at 2 years. Only 9% of patients had three-vessel disease and they had an 85% survival at 1 year. Eleven patients died and 23 had coronary bypass surgery. In this cohort of younger patients (mean age 51 years), prophylactic therapy may not be justified because of the low mortality and should be reserved for identifiable high-risk groups.
The acute hemodynamic effects of a new agent, MDL 17,043, in the treatment of congestive heart failure.
Authors: Uretsky B F , Generalovich T , Reddy P S , Spangenberg R B , Follansbee W P
Published: June 2011

MDL 17,043 administered intravenously or orally exerts positive inotropic and vasodilator actions in experimental animal preparations. We studied its acute hemodynamic effects in 15 patients with severe congestive heart failure by right-heart catheterization. Intravenous MDL 17,043 at 10 minutes increased cardiac index (3.4 +/- 0.8 vs 1.9 +/- 0.4 l/min/m2), narrowed arteriovenous oxygen content difference (4.6 +/- 0.8 vs 7.8 +/- 2.0 vol%), increased heart rate (98 +/- 14 vs 89 +/- 18 beats/min), and decreased systemic arterial (67 +/- 10 vs 83 +/- 11 mm Hg), pulmonary capillary wedge (12 +/- 5 vs 24 +/- 5 mm Hg) and right atrial (6 +/- 5 vs 12 +/- 7 mm Hg) mean pressures significantly (p less than 0.001). In 11 patients, hemodynamics were monitored hourly for 6 hours. Compared with baseline, the cardiac index and heart rate were higher and mean systemic arterial pressure was lower for 6 hours; pulmonary capillary and right atrial mean pressures were significantly lower for 5 hours. No serious arrhythmias or side effects occurred. These data suggest that MDL 17,043 may be useful for treating congestive heart failure.
A regurgitant jet and echocardiographic abnormalities in aortic regurgitation: an experimental study.
Authors: Nakao S , Tanaka H , Tahara M , Yoshimura H , Sakurai S , Tei C , Kashima T
Published: June 2011

Acute aortic regurgitation was created experimentally in 21 mongrel dogs to examine the relationship of the regurgitant jet to observed echocardiographic findings. The direction of the regurgitant jet was studied by echo contrast injections in the aortic root. Diastolic fluttering of the anterior mitral leaflet (AML) was noted in all 21 dogs irrespective of direction of the jet. Diastolic fluttering of the interventricular septum (IVS) was noted in six of the seven dogs with a tear of the noncoronary cusp and in one of seven dogs with lesions in the left coronary cusp. In all seven dogs with echocardiographically demonstrated IVS fluttering, a regurgitant jet impinged on the anterior part of the IVS. Amplitude of the AML excursion was not significantly different from control when the lesions involved the noncoronary or the left coronary cusps. However, all seven dogs that had a lesion in the right coronary cusp demonstrated a significant reduction in the amplitude of the AML excursion. The regurgitant jet in these dogs impinged uniformly on the AML. We conclude that diastolic fluttering of the AML is uniformly observed and unrelated to the direction of the regurgitant jet, diastolic fluttering of the IVS is caused by the regurgitant jet impinging upon the IVS, and amplitude of the AML may be reduced as a result of a jet impingement of the AML.
The mitral valve orifice method for noninvasive two-dimensional echo Doppler determinations of cardiac output.
Authors: Fisher D C , Sahn D J , Friedman M J , Larson D , Valdes-Cruz L M , Horowitz S , Goldberg S J , Allen H D
Published: June 2011

We developed and validated a mitral valve orifice method for Doppler cardiac output determination. In 15 open-chest dogs, cardiac output was controlled and measured by a roller pump interposed between the right atrium and pulmonary artery as a right-heart bypass. Left heart flows were measured in the open-chest dog model by Doppler measurements at the mitral valve orifice and compared not only to volume flow measured by the roller pump, but to electromagnetic flow meters as well. The maximum mitral valve orifice area was measured off short-axis two-dimensional echocardiographic views by planimetry. The maximal orifice was then adjusted for its diastolic variation in size by calculating a ratio of mean-to-maximal mitral valve separation on a derived M-mode echocardiogram. Flow was sampled parallel to mitral valve inflow in a four-chamber plane. The multiplication of mean flow throughout the cardiac cycle by the mean mitral valve area after correction for diastolic size variation yielded a cardiac output determination that could be compared to the roller pump measurement. Fifty-two cardiac output determinations over roller pump values of 1-5 l/min yielded a high correlation between roller pump flows and Doppler (r = 0.97 +/- 0.23 l/min). Our study shows that the mitral valve orifice provides an accurate site for Doppler cardiac output measurements.
Fibrinolytic effects of intracoronary streptokinase administration in patients with acute myocardial infarction and coronary insufficiency.
Authors: Cowley M J , Hastillo A , Vetrovec G W , Fisher L M , Garrett R , Hess M L
Published: June 2011

Serial coagulation studies were obtained in 25 patients treated with intracoronary streptokinase infusion for myocardial infarction (23 patients) or coronary insufficiency (two patients) to determine the frequency of systemic fibrinolytic activity. Clotting studies were obtained before and after infusion and at 4-hour intervals until normalization. Intracoronary thrombolysis was successful in 20 of 23 patients (87%) with myocardial infarction. Streptokinase dosage in this study was 201,000 +/- 74,000 IU (+/- SD). Systemic fibrinolytic activity, defined as greater than 70% reduction of fibrinogen using a functional assay (Claus method), occurred in 22 of 25 patients (88%) and was present at a mean streptokinase dosage of 119,000 +/- 52,000 IU. Fibrinogen in the total population decreased from 342 +/- 80 to 87 +/- 94 mg% (p less than 0.0001). In patients with systemic effect, the mean fibrinogen level after infusion was 17% of baseline, increased to 43% at 24 hours, and returned to normal at 30 hours. Plasminogen decreased to 7% of baseline activity after infusion (p less than 0.0001), was 44% of baseline at 24 hours, and returned to normal at 48 hours. Intraprocedural sampling during infusion showed reduction of fibrinogen by 25% after 30,000 IU (p less than 0.0005) and by 71% at 120,000 IU (p less than 0.0001); plasminogen decreased by 50% after 30,000 IU (p less than 0.0001) and by 84% at 120,000 IU (p less than 0.0001). Prothrombin time increased from 11.5 +/- 0.8 seconds to 22.0 +/- 7.8 seconds after infusion (p less than 0.0001) and returned to normal at a mean of 18 +/- 11 hours after infusion. Partial thromboplastin time was markedly prolonged (greater than 100 seconds) after infusion, returned to less than or equal to 2 times control at 5 +/- 2 hours, and returned to normal at 9 +/- 4 hours after infusion. Fibrinogen degradation products were less than 10 micrograms/ml before infusion, increased to greater than 40 micrograms/ml after infusion, and remained greater than 40 micrograms/ml in 40% of patients at 24 hours after infusion. These data indicate that systemic fibrinolytic activity occurs in a high percentage of patients with "low-dose" intracoronary streptokinase infusion and that coagulation variables may be altered for 24-48 hours after infusion.
Effect of the ouabain-quinidine interaction on left ventricular and left atrial function in conscious dogs.
Authors: Goldman S , Hager W D , Olajos M , Perrier D , Mayersohn M
Published: June 2011

The effect of the ouabain-quinidine interaction was examined in 10 conscious dogs. Left ventricular (LV) pressure, LV dP/dt, LV diameter and left atrial (LA) diameter were measured with high-fidelity micromanometers and sonomicrometer crystals. Ouabain, 0.025 mg/kg, significantly (p less than 0.05) increased LV dP/dt, LV and LA fractional shortening and LV and LA velocity of circumferential fiber shortening (Vcf). In a separate experiment, quinidine was administered as a bolus dose, 3.85 mg/kg, followed by an infusion, 0.28 mg/kg/min. This resulted in steady-state quinidine concentrations that produced no change in wall motion or hemodynamics. When ouabain was given 1 hour into the quinidine infusion, only LV dP/dt increased significantly (p less than 0.05). Ouabain alone increased LV dP/dt 26.4 +/- 3.5%, whereas ouabain during the quinidine infusion increased it by 9.5 +/- 2.3%. Similar differences were seen in the responses to ouabain in the absence and presence of quinidine: LV Vcf, 22.4 +/- 4.9% vs 6.0 +/- 2.1%, LV fractional shortening, 23.1 +/- 4.6% vs 5.8 +/- 2.1%, LA Vcf, 22.7 +/- 5.9 vs 4.6 +/- 2.0% and LA fractional shortening, 21.8 +/- 7% vs 7.8 +/- 3.3%. Thus, in the presence of quinidine the increase in intropy usually seen with ouabain was markedly attenuated. These data suggest that the quinidine-induced increase in digoxin serum concentrations is accompanied by a decrease in the contractile response of the heart to digoxin.
Mitral valve prolapse in short-term experimental coronary occlusion: a possible mechanism of ischemic mitral regurgitation.
Authors: Tei C , Sakamaki T , Shah P M , Meerbaum S , Kondo S , Shimoura K , Corday E
Published: June 2011

Experimental coronary occlusions were carried out in 12 closed-chest dogs to investigate the functional anatomic characteristics of the mitral valve complex during acute myocardial ischemia. Two-dimensional echocardiography was used to assess left ventricular function, the mitral valve complex, and left atrial size. Presence of mitral regurgitation was assessed by left ventricular contrast echocardiography. Thirty-seven coronary occlusions of up to 10 min in duration were carried out in proximal or distal locations in the left anterior descending and the left circumflex coronary arteries. Mitral regurgitation, which was mild in severity as judged by a small rise in pulmonary artery wedge pressures, was observed in 15 of 37 brief coronary occlusion experiments. Mitral valve prolapse was noted in all 15 experiments, as well as in four additional studies in which mitral regurgitation was not seen. The development of experimental mitral valve prolapse was explained by measurements that demonstrated a relative displacement of the papillary muscle tips toward the mitral orifice. We conclude that mitral valve prolapse is a common sequela of short-term coronary occlusion and is often associated with mild mitral regurgitation. Relative displacement of ischemic papillary muscles toward the mitral orifice appears to be a likely mechanism of acute ischemic mitral valve prolapse.
Canine left ventricular mass estimation by two-dimensional echocardiography.
Authors: Schiller N B , Skiôldebrand C G , Schiller E J , Mavroudis C C , Silverman N H , Rahimtoola S H , Lipton M J
Published: June 2011

This study was designed to develop a two-dimensional echocardiographic method of measuring the mass of the left ventricle. The general formula for an ellipse was used to derive an algorithm that described the shell volume of concentric truncated ellipsoids. In 10 canine left ventricular two-dimensional echocardiograms, this algorithm accurately predicted postmortem left ventricular mass (r = .98, SEE +/- 6 g) and was independent of cardiac cycle phase (systole vs diastole, r = .92).
Atrioventricular sequential pacing: differential effect on retrograde conduction related to level of impulse collision.
Authors: Mahmud R , Lehmann M , Denker S , Gilbert C J , Akhtar M
Published: June 2011

Patients with DDD pacemakers who have intact retrograde conduction are known to be at risk of developing ventricular and "endless loop" tachycardia. To address this problem, a pacing protocol was designed in which V2A2 conduction was assessed in 16 patients during ventricular pacing alone (standard method) and during paced atrioventricular (AV) sequential drive (AV sequential method); the results were then compared. In eight of 16 patients who had intact retrograde conduction with both methods (group 1), the V2A2 intervals were significantly shorter (by 60 to 340 msec) with the AV sequential method. In the remaining eight patients, who demonstrated V2A2 block with the standard method, no V2A2 block occurred with the AV sequential method. In this study, two sets of AV intervals were programmed to produce collision of the two impulses (atrial and ventricular), either in the AV node or the His-Purkinje system (HPS). The site of V2A2 facilitation was related to the site of impulse collision. These results can be explained by earlier excitation by the atrial impulse (of AV node and/or HPS) during AV sequential pacing. However, in some cases it was evident that antegrade propagation of the atrial impulse was responsible for subsequent facilitation. The data suggest that assessment of retrograde conduction in candidates for DDD pacemakers can be made most accurately by the AV sequential method.
Predictors of systolic blood pressure response to treadmill exercise: the Lipid Research Clinics Program Prevalence Study.
Authors: Criqui M H , Haskell W L , Heiss G , Tyroler H A , Green P , Rubenstein C J
Published: June 2011

We used multiple linear regression to study predictors of systolic blood pressure response (SBPR), i.e., the increase in pressure above baseline after 3, 6, and 9 min of treadmill exercise, in 4262 men and women. Predictors considered were usual SBP, the difference (delta SBP) between resting SBP and SBP immediately before exercise, age, education, obesity index, alcohol consumption, cigarette smoking, preexercise heart rate and, in women, gonadal hormone use. In men, age, obesity index, and cigarette smoking were positively associated with SBPR and in women 20 to 49 years old, age, obesity index, and alcohol consumption were positively associated with SBPR. In women 50 years old or older, usual SBP was negatively associated with SBPR. In both men and women a larger delta SBP was associated with a smaller SBPR. These results help explain the considerable variation in SBPR, and the delta SBP results suggest that potential SBPR may, to certain extent, have a specific, finite range. The similarity of predictor variables for SBPR to predictor variables for hypertension is concordant with the previous observation that a high SBPR may foreshadow subsequent hypertension.
Reduced aortocoronary sinus extraction of epinephrine in patients with left ventricular failure secondary to long-term pressure or volume overload.
Authors: Rose C P , Burgess J H , Cousineau D
Published: June 2011

Heart failure is associated with a reduction in tissue norepinephrine concentration, catecholamine fluorescence, and tyrosine hydroxylase activity. We hypothesized that this attrition of sympathetic nerve function might also be associated with a reduction in the ability of the neuronal membrane to sequester catecholamines. Since the heart does not release epinephrine, the cardiac extraction of epinephrine should be an index of the membrane uptake system. In 12 patients with documented left ventricular failure (pulmonary edema) secondary to mechanical overload and in 10 patients with no history of heart failure, we measured simultaneous plasma catecholamine concentrations in the aorta, coronary sinus, and femoral vein. The aortocoronary sinus extraction of epinephrine was 43 +/- 17% in the group with no evidence of heart failure but 0 +/- 14% in the group with failure. Net norepinephrine outflow (release minus extraction) was significantly higher in the group with failure, possibly because of reduced extraction. There was neither a reduction in the ability of the lower limb to extract epinephrine nor an increased norepinephrine outflow from the limb. These findings suggest that the sympathetic neuronal membrane uptake system is also depressed in the failing heart and that if the mechanism of catecholamine sequestration in the heart is related to that in the lower limb, the ablation of sympathetic nerve function is specific to the heart and is not a result of a generalized depression of the peripheral sympathetic nervous system.
Exercise conditioning in middle-aged men after 10 days of bed rest.
Authors: DeBusk R F , Convertino V A , Hung J , Goldwater D
Published: June 2011

Of 12 healthy men with a mean age 50 +/- 4 years who had been at bed rest for 10 days, six were randomly assigned to perform individually prescribed physical exercise daily for 60 days after bed rest (exercise group) and six simply resumed their customary activities (control group). Exercise group subjects were significantly more active than control subjects during this interval (p less than .05). Two classic training effects observed in the 60 days after bed rest were significantly larger among exercise than among control group subjects; compared with values immediately after bed rest, heart rate at a constant submaximal workload declined by 36 +/- 11 beats/min in the exercise group vs 16 +/- 8 beats/min in the control group and peak oxygen consumption increased by 4.8 +/- 4.2 vs 2.2 +/- 5.0 ml/kg/min (both p less than .05). Despite these differences in the cardiovascular response to exercise, peak oxygen consumption in both groups returned to before-bed rest levels by 30 days after bed rest, and this was accompanied by significant (p less than .05) and similar increases in resting left ventricular end-diastolic and stroke volumes in both groups. Simple resumption of usual physical activities after bed rest was as effective as formal exercise conditioning in restoring functional capacity to before-bed rest levels.
Effect of hydralazine on perfusion and metabolism in the leg during upright bicycle exercise in patients with heart failure.
Authors: Wilson J R , Martin J L , Ferraro N , Weber K T
Published: June 2011

The aerobic exercise capacity of patients with chronic heart failure is frequently impaired because of inadequate O2 transport to working skeletal muscle. To determine whether hydralazine improves O2 transport to working muscle, we examined the effect of intravenous hydralazine on blood flow (measured by thermodilution) and metabolism in the leg during maximal upright bicycle exercise in 10 patients with chronic heart failure. Hydralazine increased maximal exercise cardiac output (5.6 +/- 0.7 to 6.7 +/- 0.6 l/min; p less than .01) and decreased systemic O2 extraction (79 +/- 3% to 65 +/- 2%; p less than .01) but did not alter maximal O2 uptake (787 +/- 105 vs 779 +/- 82 ml/min). Leg blood flow at maximal exercise increased from 1.6 +/- 0.2 to 2.1 +/- 0.4 l/min (p less than .03); the proportion of cardiac output delivered to the leg remained unchanged (59 +/- 3% vs 57 +/- 9%). This increase in flow was associated with a decrease in O2 extraction in the leg (84 +/- 2% to 79 +/- 2%; p less than .01) and no change in peak femoral venous lactate (59.1 +/- 7.4 vs 54.1 +/- 5.3 mg/dl), suggesting that there is functional or anatomic shunting of the augmented limb flow rather than delivery to metabolizing muscle. These data suggest that hydralazine augments flow to the exercising limb in patients with heart failure but that this augmented flow does not increase oxygen availability within working muscle.
Factors determining the loss of ductus arteriosus responsiveness to prostaglandin E.
Authors: Clyman R I , Mauray F , Roman C , Heymann M A , Payne B
Published: June 2011

The ductus arteriosus of the newborn infant varies in its ability to dilate when doses of prostaglandin E (PGE) are administered. We infused PGE2 into 15 late-gestation newborn lambs to determine which factors regulate the ability of the ductus arteriosus to respond to PGE. PGE2 dilated the ductus in 10 lambs (responders); in five other lambs, despite similar PGE2 concentrations, there was no effect (nonresponders). The measured ductus resistance after the PGE2 infusion was directly related to the ductus resistance before the infusion. Responders had a larger left-to-right shunt through the ductus before the PGE infusion than nonresponders. Ductus that were isolated and studied in vitro from lambs that were nonresponsive to PGE2 (in vivo) were limited in their ability to relax with PGE2 as well as to actively contract with oxygen and indomethacin. This generalized loss of ductus responsiveness was directly related to the amount of the left-to-right shunt through the lumen of the ductus. These observations are consistent with the hypothesis that the constriction of the ductus arteriosus after birth limits the ability of the ductus to respond to PGE therapy.
Computerized image analysis for quantitative measurement of vessel diameter from cineangiograms.
Authors: Spears J R , Sandor T , Als A V , Malagold M , Markis J E , Grossman W , Serur J R , Paulin S
Published: June 2011

Subjective estimates of the angiographic severity of coronary artery stenoses show variability and inaccuracy. We therefore tested the accuracy of a newly developed computerized image analysis system for quantitating vessel diameter from cineangiograms. Fourteen cylindrical phantoms of known diameter were filled with contrast medium and filmed over a wide range of clinically relevant radiographic conditions in order to develop regression equations that related computer-derived to anatomic diameters. Computer measurements of vessel diameter were unaffected by vessel size, magnification, focal spot size, thickness of scattering medium, kilovolt peak, or location within the radiographic field, but a correction factor was necessary for a small but significant (p less than .01) linear dependence on contrast medium concentration. The accuracy of computerized vessel diameter measurements ranged between +/- 59 and +/- 137 mu for all conditions except for rapid vessel motion and contrast medium concentrations of 50% or less meglumine diatrizoate (Renografin 76), both of which resulted in reduced accuracy as well as in the inability to locate lumen edges of vessels less than 1 mm in diameter.
Variability in the measurement of regional left ventricular wall motion from contrast angiograms.
Authors: Sheehan F H , Stewart D K , Dodge H T , Mitten S , Bolson E L , Brown B G
Published: June 2011

Four types of variability affecting quantification of regional wall motion from contrast left ventriculograms (LVgrams) were studied. These included beat-to-beat variability in 24 LVgrams, intraobserver and interobserver variability in 20 LVgrams, and study-to-study variability in serial LVgrams of 21 patients with stable coronary artery disease. Motion was measured at 100 equidistant chords perpendicular to a center line drawn midway between the end-diastolic and end-systolic contours and normalized for heart size. Variability was computed as the absolute difference between observations. Beat-to-beat, intraobserver, and interobserver variability at the 100 chords were similar, averaging 14%, 14%, and 17%, respectively, of the mean motion in 64 patients with normal ventriculograms. Study-to-study variability was significantly higher, averaging 30% of mean normal motion, but was reduced when regional motion was calculated as the mean motion of chords within a region of interest. Variability peaked at the apex. Realignment to correct for cardiac rotation significantly increased variability. Investigators whose methods of wall motion analysis rely on identification of the apex as a landmark should be aware of this source of potential variability and error.
Reentrant ventricular arrhythmias in the late myocardial infarction period. Interruption of reentrant circuits by cryothermal techniques.
Authors: El-Sherif N , Mehra R , Gough W B , Zeiler R H
Published: June 2011

Both sustained and nonsustained ventricular tachycardias were reproducibly induced in dogs 3 to 5 days after ligation of the left anterior descending coronary artery. Isochronal maps of ventricular activation were constructed from close bipolar electrograms recorded from the entire epicardial surface and selected intramural sites by a computerized multiplexing technique. The electrophysiologic data were correlated with the anatomic characteristics of the infarction. The induced tachycardias were due to reentrant activation in the surviving epicardial layer overlying the infarction. Cooling or cryoablation was applied to localized epicardial sites along the reentrant circuit to reversibly or permanently interrupt reentrant activation. The reentrant circuit could be consistently interrupted when cooling or cryoablation was applied to the distal part of the common reentrant wave front proximal to the site of earliest reactivation. Localized cooling of the site of earliest reactivation usually failed to interrupt reentry because the common reentrant wave front reactivated other sites close to the original reactivation site. Before interruption of reentry, cooling resulted in characteristic changes in conduction of the reentrant wave front. The study (1) fulfills Mines' criteria that circus movement reentry is the mechanism of the induced rhythms in this canine experimental model and (2) identifies the critical site along the reentrant circuit at which cryothermal ablation (or surgical interruption) of reentrant activation could be successfully accomplished.
Ectopic left atrial rhythm that produces QRS changes in absence of Wolff-Parkinson-White syndrome.
Authors: Zaman L , Garcia N , Luceri R M , Castellanos A , Myerburg R J
Published: June 2011

In an 18-year-old patient without manifest or concealed Wolff-Parkinson-White syndrome, spontaneous and paced left atrial impulses penetrated a left-sided AV nodal input and thereafter activated the ventricles in a normal fashion exclusively through the His-Purkinje system. On the other hand, sinus and paced right atrial impulses entered a right-sided atrioventricular nodal input that was completely dissociated from the left-sided input to subsequently activate the ventricles partly through Mahaim fibers and partly through the His-Purkinje system. The Mahaim fibers, which acted as "bystanders" during episodes of atrioventricular nodal reciprocating tachycardia, seemed to have extended from a "distal," common (right-sided) intranodal pathway (or "proximal" His bundle) to the right ventricle or, although this is less likely, to the right bundle branch. More studies are necessary to determine whether the association on the surface electrocardiogram of an ectopic slow left atrial rhythm with changes in QRS morphology (but not in QRS duration) always reflects the existence of Mahaim fibers.
Miscuffing: inappropriate blood pressure cuff application.
Authors: Manning D M , Kuchirka C , Kaminski J
Published: June 2011

For the accurate indirect measurement of blood pressure (BP), the American Heart Association (AHA) now recommends that cuff size should be based solely on limb circumference. We studied prevailing cuffing habits and compared them with newly revised AHA guidelines. Monitoring our staff's cuff applications, we found that "miscuffing" occurred in 65 (32%) of 200 BP determinations on 167 unselected adult outpatients, including 61 (72%) of 85 readings taken on "nonstandard" size arms. Undercuffing large arms was the most frequent error, accounting for 84% of the miscuffings. Considering that miscuffing distorts BP readings by an average of 8.5 mm Hg systolic and 4.6 mm Hg diastolic, we can improve the accuracy of our BP determinations by remarking our cuffs and using the new AHA guidelines.
Long-term exercise performance after percutaneous transluminal coronary angioplasty and coronary artery bypass grafting.
Authors: Meier B , Gruentzig A R , Siegenthaler W E , Schlumpf M
Published: June 2011

In our first 169 consecutive patients admitted to undergo percutaneous transluminal coronary angioplasty (PTCA) serial bicycle ergometric exercise sessions were scheduled to assess long-term-exercise performance. In 160 of these 169 patients (95%) an average of seven ergometric measurements were available during a mean follow-up period of 29 months (range 1 to 60 months). Two groups were formed. One consisted of 132 patients in whom PTCA was successful and the other consisted of 28 patients with failure of PTCA who subsequently underwent coronary artery bypass grafting (CABG) either on an emergency basis (12 patients) or as an elective procedure (16 patients). Exercise performance was expressed as work capacity in watts according to the highest completed exercise stage. In the successful PTCA group the actual work capacities increased from 74 +/- 42 W (mean +/- SD) before PTCA to 122 +/- 47 W at the most recent follow-up examination. In patients who underwent emergency or elective CABG the respective figures were 73 +/- 34 or 65 +/- 37 W before surgery and 120 +/- 41 or 119 +/- 41 W at the most recent follow-up examination (p less than .005 for all preprocedure to postprocedure comparisons). Successful PTCA and CABG after failed PTCA improve work capacity significantly. Comparison of our results with those of surgical studies indicates that a failed attempt at PTCA before CABG does not compromise the functional outcome of the operation, regardless whether it is done on an emergency or on an elective basis.
Action of sotalol on potential reentrant pathways and ventricular tachyarrhythmias in conscious dogs in the late postmyocardial infarction phase.
Authors: Cobbe S M , Hoffman E , Ritzenhoff A , Brachmann J , Kübler W , Senges J
Published: June 2011

Sotalol is a beta-adrenergic blocker that also prolongs action potential duration and myocardial refractoriness over the short term (class III effect). Its short-term antiarrhythmic effects were compared with those of metoprolol, which has neither short-term class III nor membrane-stabilizing action, on reentrant ventricular arrhythmias produced by programmed stimulation in 17 conscious dogs 3 to 8 days after myocardial infarction. Ventricular arrhythmias were prevented or significantly slowed by sotalol in 11 of 19 studies (58%) compared with in one of 14 (7%) studies with metoprolol. Sotalol prolonged refractoriness in the infarct zone, measured from an implanted "composite" electrode, by 41 +/- 45% (mean +/- SD, p less than .01), which was significantly greater than the increases it produced in effective refractory period of the normal ventricle (14.0 +/- 5.5%) or QT interval (12.5 +/- 7.8%). Metoprolol had no effect on infarct-zone refractoriness. Sotalol differentially increases refractoriness in potential reentry circuits in ischemic myocardium. Its antiarrhythmic effect in this model is not due to beta-blockade, and is presumably related to prolongation of action potential duration.
Artificial hearts and blood pumps in the treatment of profound heart failure.
Authors: Pierce W S
Published: June 2011

The recent clinical use of a pneumatic artificial heart at the University of Utah has focused attention on the role of blood pumps in the support of the circulation. Pneumatically powered assist pumps are now in clinical trials in patients with profound but reversible heart failure after open-heart surgery; survival rates as high as 50% in a heretofore lethal condition have been encouraging. The results of animal studies with the pneumatic artificial heart suggest that these devices are ready for clinical trials; the major application is likely to be as a bridge to cardiac transplantation. Implantable electric motor-driven assist pumps and artificial hearts are being evaluated in animals as permanent cardiac support or replacement devices; clinical use is projected to begin late in this decade. Initially, these devices will be employed in patients with end-stage cardiac disease who are not suitable candidates for cardiac transplantation or for whom donor hearts are not available. The availability of compact blood pumps will offer new forms of therapy to patients with certain types of profound heart failure.
Effects of low-dose dobutamine on coronary hemodynamics, myocardial metabolism, and anginal threshold in patients with coronary artery disease.
Authors: Pacold I , Kleinman B , Gunnar R , Loeb H S
Published: June 2011

Fourteen patients with coronary artery disease and normal or near-normal left ventricular function were studied at rest and during atrial pacing until the occurrence of angina (12 patients) before and during infusion of dobutamine (3.80 +/- 0.45 micrograms/kg/min). At rest, during the infusion, three patients developed chest pain, mean ST segment depression increased from 0.02 to 0.08 mV (p less than .001), and myocardial lactate extraction fell from +17.5% to -1.4% (p less than .05). These ischemic changes were associated with significant increases in arterial systolic pressure (134 to 149 mm Hg), heart rate (79 to 91 beats/min), coronary sinus flow (89 to 113 ml/min), and myocardial oxygen consumption (10.8 to 13.5 cc/min). In contrast, during atrial pacing, dobutamine did not reduce the pacing threshold or further increase myocardial oxygen consumption or ST segment changes; however, arterial mean and diastolic pressures were significantly lower with pacing during dobutamine infusion compared with control pacing. In the absence of heart failure, dobutamine in low doses can cause myocardial ischemia in patients with coronary artery disease. The absence of increased ischemia from dobutamine during pacing may reflect reversal of pacing-induced ventricular dysfunction.
Treatment of restenosis of coarctation by percutaneous transluminal angioplasty.
Authors: Kan J S , White R I , Mitchell S E , Farmlett E J , Donahoo J S , Gardner T J
Published: June 2011

Percutaneous transluminal angioplasty (PTA) was used successfully to treat coarctation restenosis in seven patients. The patients were 10 months to 17 years old at the time of the angioplasty, and the initial coarctation repair had been performed 10 months to 16 1/2 years previously. PTA reduced the systolic pressure gradient across the coarctation from a mean of 58 mm Hg before the procedure to a mean of 13 mm Hg immediately after PTA. Follow-up has been from 1 to 14 months and indicates that the decrease in the systolic pressure gradient is persistent.
Intra-aortic balloon pumping in infants and children.
Authors: Veasy L G , Blalock R C , Orth J L , Boucek M M
Published: June 2011

From November 1981 to November 1982, intra-aortic balloon pumping (IABP) was used after surgery in eight patients who were from 6 weeks to 6 years old and who weighed from 4.2 to 16.2 kg. In seven patients, specially constructed intra-aortic balloons with 2.5 and 5.0 ml volumes mounted on No. 5F catheters were used. In the largest and oldest patient, a two-chamber 10 ml balloon was used. The pumping module used was the Datascope System 82. Effective diastolic augmentation of arterial pressure was accomplished in seven of the eight patients and suprasystolic diastolic augmentation was accomplished in four. The two youngest and smallest patients are the only long-term survivors. There were two short-term survivors who died 5 and 10 days after successful IABP. In only one patient was there no appreciable effect of IABP. Miniaturization of the equipment has permitted IABP to be used effectively in pediatric patients.