bluuebunny/crossref_metadata_2025 huggingface dataset:
Interference of calcium entry blockade in vivo with pressor responses to alpha-adrenergic stimulation: effects of two unrelated blockers on responses to both exogenous and endogenously released norepinephrine.
Authors: Pedrinelli R , Tarazi R C
Published: June 2011

To the extent that calcium availability is the final common mediator of vasoconstrictor responses, calcium entry blockade might interfere with physiologic responses to adrenergic stimulation. To test this hypothesis, we studied the effects of calcium entry blockade on pressor responses to norepinephrine in pithed, normal Sprague-Dawley rats in two different ways: (1) by evaluating the effects on pressor responsiveness to exogenous norepinephrine during differential blockade of alpha 1-(prazosin, 0.3 mg/kg) and of alpha 2-receptors (yohimbine, 0.3 mg/kg) and (2) by comparing the effects of calcium entry blockade with those of prazosin and those of rauwolscine (a specific alpha 2-antagonist) on pressor responses to infusions of both endogenously released norepinephrine (electrical stimulation of the pithing rod) and exogenous norepinephrine. In the presence of alpha 1-blockade, both nitrendipine (0.01 mg/kg) and verapamil (0.6 mg/kg) shifted the norepinephrine pressor dose-response curve to the right but were ineffective in alpha 2-blocked animals. Furthermore, nitrendipine (range 0.01 to 0.3 mg/kg) proved to be more effective (p less than .001) against exogenous norepinephrine than against electrical stimulation of the spinal cord, a behavior opposite that of selective alpha 1-blockade (prazosin) and directionally comparable to that of selective alpha 2-antagonism (rauwolscine). These data indicate that calcium entry blockade in vivo preferentially antagonizes the alpha 2-pressor component of exogenous norepinephrine. In addition, both calcium entry blockers were consistently more active (p less than .01) than rauwolscine (0.01 to 1 mg/kg) in antagonizing the pressor response to neural stimulation, suggesting that mechanisms different from "classical" alpha 2-antagonism may also contribute to the overall effect of calcium entry blockade on the adrenergic control of peripheral vascular tone.
Transient predominant right ventricular ischemia caused by coronary vasospasm.
Authors: Parodi O , Marzullo P , Neglia D , Galli M , Distante A , Rovai D , L'Abbate A
Published: June 2011

This study describes the clinical experience with four patients with variant angina caused by spasm of the right coronary artery who were assessed for evidence of right ventricular involvement. The patients were suspected of having predominant right ventricular ischemia on the basis of normal thallium-201 scans, left ventricular ejection fraction, regional wall motion assessed by equilibrium radionuclide angiography (RNA), two-dimensional echocardiographic findings, and left ventricular hemodynamics; all procedures were performed during transient ST segment elevation in the inferior leads. Right ventricular ischemia was documented in four patients by first-pass radionuclide studies and phase analysis of RNA, and in three patients by simultaneous right and left hemodynamic monitoring. The clinical findings from these four patients are compared with those from four other patients with similar electrocardiographic changes, coronary anatomic distribution, and documented right coronary spasm but with evidence of left ventricular involvement as documented by abnormal thallium-201 scintigraphy, RNA, two-dimensional echocardiography, and left hemodynamics during ischemic episodes. Although preliminary, these data indicate the existence of prevalent right ventricular ischemia during variant angina caused by right coronary vasospasm. This condition should be suspected whenever typical anginal symptoms and/or ischemic electrocardiographic changes are accompanied by normal thallium-201 scintigraphic findings and/or normal left ventricular function as assessed by RNA, echocardiography, and left hemodynamic monitoring. Among noninvasive procedures, first-pass radionuclide study and phase analysis of RNA represent suitable techniques for detecting transient right ventricular dysfunction.
Influence of two-stage anatomic correction on size and distensibility of the anatomic pulmonary/functional aortic root in patients with simple transposition of the great arteries.
Authors: Sievers H H , Lange P E , Arensman F W , Radley-Smith R , Yacoub M H , Harms D , Heintzen P H , Bernhard A
Published: June 2011

To evaluate the results of the two-stage anatomic correction of simple transposition of the great arteries the size, distensibility, and histologic characteristics of the anatomic pulmonary root, which arises from the anatomic left ventricle and which we termed the functional aortic root after anatomic correction, were determined in seven patients before and twice after anatomic correction (mean 43 and 671 days) and the results were compared with those in normal control subjects. The diameter of the systolic sinus of the anatomic pulmonary root increased after banding on the average to 140% of normal, whereas the diameter of the diastolic sinus of the functional aortic root increased after anatomic correction on the average to 150% of normal. Diameters of both the systolic and diastolic sinuses of the functional aortic root remained 30% to 55% larger than normal after anatomic correction. Growth potential of the functional aortic root after anatomic correction was normal, whereas its distensibility, as assessed by determination of the percent change in radius and pressure-strain elastic modulus (stiffness index), was decreased after anatomic correction. This pressure-strain elastic modulus was directly related to the corresponding body surface area and age at banding. In four of five specimens of the anatomic pulmonary arterial wall that were obtained at the time of anatomic correction, fragmentation and shortening of elastic fibers were observed. The histologic characteristics of the pulmonary root in the patient with the smallest body surface area at banding and normal distensibility of the anatomic pulmonary/functional aortic root before and after anatomic correction revealed normal aortic configuration of the elastic tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
Computer interpretation of pediatric orthogonal electrocardiograms: statistical and deterministic classification methods.
Authors: Brohet C R , Robert A , Derwael C , Fesler R , Stijns M , Vliers A , Braasseur L A
Published: June 2011

Statistical multivariate and conventional deterministic methods of computerized interpretation of the electrocardiogram (ECG) were compared in the analysis of 1711 pediatric orthogonal ECGs validated by nonelectrocardiographic criteria on the basis of clinical and anatomic diagnoses. Among 642 children catheterized for the evaluation of congenital heart disease, there were 140 patients with left ventricular hypertrophy, 299 with right ventricular hypertrophy, and 203 with biventricular hypertrophy. A group of 1069 obviously healthy school children was studied as a control. The overall accuracy of multigroup ECG diagnosis was 85% and 79% for the statistical and deterministic methods, respectively. The diagnostic performances of both methods expressed in terms of sensitivity and predictive value were the highest for normal children and those with right ventricular hypertrophy and lowest for children with biventricular hypertrophy. The statistical method was more sensitive in the diagnosis of left ventricular hypertrophy (74% vs 64%), right ventricular hypertrophy (86% vs 83%), and biventricular hypertrophy (62% vs 50%). Mutual agreement for a correct diagnosis by the two methods was 83% for normal children and 82% for those with right ventricular hypertrophy but only 61% for children with left ventricular hypertrophy and 39% for those with biventricular hypertrophy. In conclusion, better classification results are obtained with statistical multivariate techniques as compared with conventional deterministic analysis, but both methods of ECG interpretation are complementary and their combination in the same electrocardiographic computer program can improve diagnostic accuracy.
Coil embolization of congenital thoracic vascular anomalies in infants and children.
Authors: Fuhrman B P , Bass J L , Castaneda-Zuniga W , Amplatz K , Lock J E
Published: June 2011

When significant thoracic vascular anomalies occur in children, they may present surgical difficulties making operative management undesirable. The recent development of a new, accurate coil-delivery system has enabled us to embolize 17 vessels in five children by passing Gianturco steel coils coated with thrombogenic Dacron strands through No. 5 or 6F end-hole catheters suitable for infants. Coils of 0.038 inch packed diameter were fed through the catheter lumen by a flexible guidewire emerging as 3, 5, or 8 mm diameter loose coils. Fifteen of 17 vessels were successfully occluded. No complications or errors in placement of coils occurred. Four of five children clearly benefitted from the procedure. One died in spite of partial occlusion. Coil embolization can be performed accurately and safely even in small infants with a high rate of successful occlusion and may prove to be a valuable adjunct to operative management.
Advance prediction of transthoracic impedance in human defibrillation and cardioversion: importance of impedance in determining the success of low-energy shocks.
Authors: Kerber R E , Kouba C , Martins J , Kelly K , Low R , Hoyt R , Ferguson D , Bailey L , Bennett P , Charbonnier F
Published: June 2011

The purposes of this study were to evaluate a method that predicts transthoracic impedance in advance of defibrillating shocks in humans and to assess the importance of transthoracic impedance in low-energy defibrillation. Via defibrillator electrodes we applied 31 kHz current to the chest during the defibrillator charge cycle, before the defibrillating shock was actually delivered. The current flow was limited by transthoracic impedance; a microprocessor monitored the predischarge current flow and determined the predischarge impedance by calibration against known resistance values. Actual impedance to the defibrillating shock was also determined and compared with the predicted impedance. With this approach we predicted impedance in 19 patients who received 66 shocks for ventricular and atrial arrhythmias. Predicted impedance (y) correlated very well with actual impedance (x):y = .90x + 11.3; r = .97. To determine the importance of impedance in defibrillation and cardioversion, we prospectively gathered data from 96 patients who received shocks of various energies for ventricular or atrial arrhythmias. In patients with high transthoracic impedance (greater than 97 omega), low-energy shocks (less than or equal to 100 J) for ventricular defibrillation had only a 20% success rate as opposed to a 70% success rate for low-energy shocks in patients with low or average impedance (p less than .05). We conclude that transthoracic impedance can be accurately predicted in advance of defibrillation and cardioversion. This method permits the preshock identification of patients with high impedance in whom attempts to defibrillate with low-energy shocks are inappropriate.
The obstructive subaortic conus.
Authors: Waldman J D , Schneeweiss A , Edwards W D , Lamberti J J , Shem-Tov A , Neufeld H N
Published: June 2011

Eleven children are reported who had stenosis under a malposed aorta with gradients of 20 to 76 mm Hg between the right ventricle and aorta. The subaortic obstruction was caused by hypertrophy of the foreshortened infundibulum and malalignment of the infundibular septum relative to the remainder of the ventricular septum. Of these 11 patients, nine had a ventricular septal defect and seven had coarctation of the aorta. Rightward deviation of the infundibulum and aorta produced an unusually long left main coronary artery that was compressed by the stent of a bioprosthetic conduit valve in one patient. Serial cardiac catheterization studies in four patients showed progressive stenosis in each. Subaortic stenosis can develop in patients with malposition of the aorta and the frequency may be greater than 5% since milder forms are likely to occur. The obstruction can be progressive. The left coronary artery may be particularly vulnerable to compression after operative repair with an extracardiac conduit.
Concealed conduction in accessory atrioventricular pathways: an important determinant of the expression of arrhythmias in patients with Wolff-Parkinson-White syndrome.
Authors: Klein G J , Yee R , Sharma A D
Published: June 2011

Concealed conduction into accessory atrioventricular pathways has been postulated to explain variability of R-R intervals during atrial fibrillation in patients with Wolff-Parkinson-White syndrome. We examined the occurrence of concealed conduction into atrioventricular pathways using extrastimulus techniques in 26 consecutive patients undergoing electrophysiologic studies for the Wolff-Parkinson-White syndrome. Anterograde pathway concealment was demonstrated (10 patients) by introducing a second atrial extrastimulus (A3) after block in the accessory pathway occurred following the first extrastimulus (A2). The apparent effective refractory period (ERP) of the atrioventricular pathway with A3 (after A2 blocked in the pathway), or ERPB, was always greater than the ERP of the atrioventricular pathway (505 +/- 100 vs 323 +/- 105 msec, mean +/- SD; p less than .001), a finding explained by concealment into the pathway by the blocked A2. A measure of the apparent prolongation of refractoriness due to anterograde concealment (delta ERPB), defined as the difference between ERP and ERPB at a given cycle length, was derived. The average R-R interval in atrial fibrillation correlated better with delta ERPB (r = .8, p less than .01) than with the ERP (r = .6, p = NS), supporting the influence of anterograde atrioventricular pathway concealment in modulating the ventricular response during atrial fibrillation. By similar techniques, concealed retrograde conduction in the atrioventricular pathway could be demonstrated in 16 of 26 patients. In two of these patients "bystander" atrioventricular pathway conduction during orthodromic reciprocating tachycardia that did not involve the atrioventricular pathway did not occur, even though the ERP of the pathway should have permitted it, a finding readily explained by repetitive retrograde concealment into the atrioventricular pathway during tachycardia. Concealed conduction can be demonstrated in most patients with Wolff-Parkinson-White syndrome and is an important factor in the clinical expression of their arrhythmias.
Study of the infradiaphragmatic total anomalous pulmonary venous connection with cross-sectional and pulsed Doppler echocardiography.
Authors: Cooper M J , Teitel D F , Silverman N H , Enderlein M A
Published: June 2011

We studied neonates with the infradiaphragmatic form of total anomalous pulmonary venous drainage by a combination of cross-sectional echocardiography and pulsed Doppler ultrasound. The diagnosis by ultrasound was made prospectively in all six patients. Three large vascular channels could be observed passing through the diaphragm from the subcostal parasagittal plane. The vessels were identified as the descending aorta (to the left), the inferior vena cava (to the right), and the anomalous pulmonary venous channel (in the center). The vessels were insonated in turn, with pulsed Doppler ultrasound, and the characteristic normal flow signals in the aorta and inferior vena cava were obtained. The signal from the anomalous pulmonary vein was a continuous venous signal, the direction of flow being away from the heart. Pulsed Doppler ultrasound allows accurate recognition of the anomalous pulmonary venous channel without the use of contrast echocardiography.
Prospective identification of patients with amyloid heart disease by two-dimensional echocardiography.
Authors: Nicolosi G L , Pavan D , Lestuzzi C , Burelli C , Zardo F , Zanuttini D
Published: June 2011

The purpose of this study was to determine whether changes in myocardial wall echogenicity that suggest amyloid disease could be prospectively identified by a qualitative analysis of two-dimensional echocardiographic images. Two thousand seventy-eight consecutive echocardiograms obtained over a 14 month period were prospectively analyzed. The myocardial walls of 30 patients showed multiple, discrete, small highly refractive echoes; amyloid disease was not known or suspected in any of them. It was recommended that all 30 patients undergo gingival biopsy to confirm the diagnosis and biopsy was performed in 15 patients. The recommendation for biopsy was made only on the basis of two-dimensional echocardiographic images and was independent of findings regarding thickness of the walls or the dimensions of the cardiac chambers. Results of biopsy were positive in 11 patients and negative in four. We conclude that qualitative evaluation of two-dimensional echocardiographic images can identify changes in myocardial wall echogenicity that correlate with a result of gingival biopsy positive for amyloidosis. In patients who have a typical myocardial texture by two-dimensional echocardiography and a positive gingival biopsy result, cardiac amyloidosis should be strongly suspected.
Echocardiographic evaluation of the response to afterload stress test in young asymptomatic patients with chronic severe aortic regurgitation: sensitivity of the left ventricular end-systolic pressure-volume relationship.
Authors: Branzi A , Lolli C , Piovaccari G , Rapezzi C , Binetti G , Specchia S , Zannoli R , Magnani B
Published: June 2011

The detection of myocardial depression is an important goal in the management of patients with chronic severe aortic regurgitation but may be quite difficult at an early stage by the conventional basal measures of contractility. The response to afterload stress determined by angiotensin challenge and the end-systolic pressure-volume relationship was evaluated echocardiographically in 16 asymptomatic or mildly symptomatic patients with chronic severe aortic regurgitation, ages 15 to 56 years (mean 32 +/- 12). Nine normal subjects, ages 25 to 41 years (mean 31 +/- 5), served as a control group. In the group with aortic regurgitation, end-systolic dimensions were greater than 55 mm in five of 16 patients and fractional shortening was 25% or less in two of 16. In the control group angiotensin caused a decrease of stroke volume index in six out of nine patients (15% at the most) and a mild increase in three. In the group with aortic regurgitation stroke volume index decreased by 15% or more of the basal value in nine of 16 patients and increased or decreased by less than 15% in seven of 16. Ejection fraction decreased in both groups, from 61 +/- 6% to 52 +/- 7% in the control group and from 56 +/- 6% to 45 +/- 5% in the group with aortic regurgitation. Ventricular function curves were derived by relating end-diastolic volume index to stroke work index; seven of 16 patients had abnormal responses reflecting an afterload mismatch.(ABSTRACT TRUNCATED AT 250 WORDS)
Percutaneous transluminal angioplasty of the arteries of the lower limbs: a 5 year follow-up.
Authors: Gallino A , Mahler F , Probst P , Nachbur B
Published: June 2011

A total of 482 percutaneous transluminal angioplasties (PTAs) of the arteries of the lower limbs were performed in 411 patients between 1977 and 1983. The 5 year patency rate, calculated by the life table method, was 83% for iliac and 58% for femoropopliteal PTA. Clinical improvement after the procedure was confirmed by a significant drop of the arm-ankle pressure difference: 48 +/- 5 mm Hg before vs 17 +/- 5 mm Hg 2 years after iliac PTA (p less than .01) and 73 +/- 5 mm Hg before vs 28 +/- 6 mm Hg after femoropopliteal PTA (p less than .01). The majority of reocclusions occurred within the first year after angioplasty. Patients with stenoses or occlusions of less than 3 cm had a favorable long-term patency rate of 74%. Conversely, patients with femoropopliteal occlusions presenting with pain at rest, diabetes, occlusions of greater than 3 cm, or poor distal runoff had an elevated rate of reocclusion. Complications, which occurred in 8% of the patients in whom PTA was attempted, included local hemorrhage, dissection, embolism, and spasm necessitating surgical intervention in 2%. No deaths or amputations were a direct consequence of PTA. PTA of arteries of the lower limbs may thus be regarded as a valid complementary treatment to vascular surgery in patients with occlusive disease of the peripheral arteries.
Body surface late potentials: effects of endocardial resection in patients with ventricular tachycardia.
Authors: Marcus N H , Falcone R A , Harken A H , Josephson M E , Simson M B
Published: June 2011

We studied 37 patients undergoing endocardial resection for medically refractory ventricular tachycardia (VT). Each was studied before and after surgery by programmed ventricular stimulation and signal-averaged electrocardiography. Low-amplitude late potentials were identified preoperatively in 76% of patients. In the 24 patients without postoperative VT the effect of surgery was to shorten the filtered QRS duration (137 +/- 27 to 121 +/- 26 msec; p = .003), increase the voltage in the last 40 msec of the filtered QRS (16.5 +/- 16.1 to 39.0 +/- 29.4 microV; p = .003), and decrease the incidence of late potentials (71% to 33%; p = .03). The filtered QRS complex was unchanged in 13 patients whose VT persisted after surgery. No preoperative variable predicted which patients would not have inducible VT after surgery. However, loss of a late potential after surgery in nine of 10 patients was associated with absence of inducible VT (p less than .02). Loss of a late potential was not necessary for surgical success. Eight of 18 patients with a persistent late potential did not have inducible VT. The signal-averaged electrocardiogram predicted a successful outcome after endocardial resection if the late potential was no longer present.
A new scintigraphic method for determining left ventricular volumes.
Authors: Nichols K , Adatepe M H , Isaacs G H , Powell O M , Pittman D E , Gay T C , Begg F R
Published: June 2011

A new scintigraphic count-based method for measuring absolute left ventricular volumes is presented. It is a fast and simple technique that allows geometrical assumptions to be avoided and is free of radiation attenuation corrections. This method requires the acquisition of an image of the left ventricle in the right anterior oblique projection and the collection of gated blood pool images in the left anterior oblique projection. To assess the accuracy of the method scintigraphic stroke volumes were compared with those derived from thermodilution measurements during cardiac catheterization in 20 subjects, and to assess its precision the technique was applied to phantom data of known radionuclide volumes. Excellent correlations were found between the scintigraphic and both the thermodilution (r = .98) and phantom data (r = .99). The reproducibility (r = .97) of results was investigated by repeating data acquisition and analysis for 15 subjects on two different days, and the interobserver variability (r = .97) of the method was studied by having two computer operators calculate volumes for the same patient data for 20 randomly selected studies.
Decreased contractility of the ductus arteriosus in experimental pulmonic stenosis.
Authors: Mahony L , Clyman R I , Heymann M A
Published: June 2011

Delayed closure of the ductus arteriosus after birth has been observed in newborn infants with critical pulmonic stenosis and in newborn lambs with experimental pulmonic stenosis. This delayed ductal closure may be caused by a decreased ability of the muscle to contract when exposed to oxygen or to an increased production of or sensitivity to prostaglandin (PG) E2, the endogenous ductus arteriosus vasodilator. To determine whether the abnormal hemodynamic pattern during fetal life associated with pulmonic stenosis alters the responsiveness of the ductus arteriosus, we operated on 10 fetal lambs of gestational ages 70 to 77 days (term is 148 days) and placed a band around the pulmonary artery. Catheterization at 137 to 142 days showed severe pulmonic stenosis. We then studied isolated rings of ductus arteriosus from these lambs. The oxygen-induced increase in tension in rings of ductus arteriosus from lambs with pulmonic stenosis was significantly decreased (2.55 +/- 0.38; n = 10) compared with rings from control lambs (4.03 +/- 0.51; n = 6, p less than .03). There was no difference between the two groups in either the amount of PGE2 released by the rings or in the sensitivity (expressed as median effective dose) of the rings to PGE2. There was also no difference in the increase in tension when endogenous PGE2 was inhibited by indomethacin. We conclude that delayed closure of the ductus arteriosus in lambs with experimental pulmonic stenosis is not caused by increased sensitivity to or production of PGE2 in the ductus arteriosus (as it is in premature lambs) but rather is the result of a diminished ability of the ductus arteriosus to contract when exposed to oxygen.
Coronary thrombolysis with recombinant human tissue-type plasminogen activator.
Authors: Gold H K , Fallon J T , Yasuda T , Leinbach R C , Khaw B A , Newell J B , Guerrero J L , Vislosky F M , Hoyng C F , Grossbard E
Published: June 2011

The thrombolytic potency and myocardial infarct--sparing potential of recombinant tissue-type plasminogen activator (rt-PA) were studied in electrocardiographically monitored, open-chest, anesthetized dogs. Localized coronary thrombosis was produced in the left anterior descending artery by endothelial injury and instillation of thrombin and fresh blood. After 2 hr of stable thrombotic occlusion, rt-PA was infused intravenously. At a dose of 4.3 micrograms/kg/min, time to reperfusion was greater than 40 min (n = 3). However, at higher infusion rates a linear, dose-dependent time to coronary reperfusion was obtained (r = .88): at 10 micrograms/kg/min reperfusion occurred after 31 +/- 2 min (n = 3), at 15 micrograms/kg/min it was at 26 +/- 7 min (n = 4), and at 25 micrograms/kg/min, lysis was accomplished within 13 +/- 3 min (n = 3). Thrombolysis was not associated with alterations in either plasma hemostatic factors (fibrinogen, plasminogen, and alpha 2-antiplasmin) or in systemic blood pressures. Epicardial electrographic measurements revealed a significant reduction in ST elevation in all reperfused hearts. A randomized, blinded study was also carried out with 15 micrograms/kg/min of rt-PA saline in 18 dogs with 30 min of coronary thrombosis. Reperfusion in the treated group occurred after 28 +/- 3 min. No evidence of thrombolysis was noted in the saline-treated group within 240 min. Size of myocardial infarction was determined by triphenyl tetrazolium chloride staining and planimetry. Infarction involved 2.5 +/- 0.5% of the left ventricular wall in the group receiving rt-PA, but 16 +/- 3% of the left ventricle in the saline-treated group (p = .001). It is concluded that intravenous infusion of rt-PA results in rapid, dose-dependent coronary thrombolysis without systemic fibrinolytic activation and that early lysis of coronary thrombi is associated with substantial salvage of myocardial tissue.
Right heart function during left heart assist and the effects of volume loading in a canine preparation.
Authors: Farrar D J , Compton P G , Dajee H , Fonger J D , Hill J D
Published: June 2011

A significant fraction of patients in whom mechanical left ventricular assist devices are implanted for refractory cardiac failure after open heart surgery have had the complication of right heart failure. To evaluate the effects of left ventricular assistance and pressure unloading on right ventricular function, we performed experiments in the normal hearts of open-chest, anesthetized, large mongrel dogs. We compared right ventricular function before and after left ventricular-to-aortic bypass with a roller pump at right atrial pressure levels of 1, 3, 5, and 7 mm Hg produced by volume loading. No significant changes were found in cardiac output or stroke volume over this range of right atrial pressures when comparing that before to that during left ventricular bypass, which at a right atrial pressure of 1 mm Hg reduced peak left ventricular pressure from 96 +/- 6 to 15 +/- 9 mm Hg and at a right atrial pressure of 5 mm Hg reduced it from 113 +/- 3 to 29 +/- 12 mm Hg, while maintaining aortic pressure. There was no evidence of right ventricular failure under these conditions: (from before to during bypass) at a right atrial pressure of 1 mm Hg cardiac output was 3.4 +/- 0.4 to 3.7 +/- 0.6 liter/min and stroke volume was 28 +/- 5 to 33 +/- 6 ml; during volume loading at a right atrial pressure of 7 mm Hg cardiac output was 5.6 +/- 0.6 to 5.7 +/- 0.7 liter/min and stroke volume was 47 +/- 5 to 52 +/- 5 ml.(ABSTRACT TRUNCATED AT 250 WORDS)
Validation of quantitation of regional myocardial blood flow in vivo with 11C-labeled human albumin microspheres and positron emission tomography.
Authors: Wilson R A , Shea M J , De Landsheere C M , Turton D , Brady F , Deanfield J E , Selwyn A P
Published: June 2011

Use of radiolabeled microspheres is a standard method to measure regional myocardial perfusion in animals. Human albumin microspheres have been given safely to patients, but positron-emitting 68Ga-labeled human albumin microspheres are characterized by an unstable radiolabel. A new labeling procedure that covalently binds 11C (t1/2 = 20.3 min) to human albumin microspheres via 11CH3I was developed. Seven open-chest and two closed-chest dogs were studied. Reference and 11C-labeled human albumin microspheres (2 to 25 mCi) were both injected into the left atrium. Positron tomographic images were obtained of the myocardial distribution of the 11C-labeled microspheres. Timed arterial withdrawal was used for both reference gamma-labeled microspheres and 11C-labeled human albumin microspheres. Myocardial tissue samples matched to tomographic slices were well-counted for calculation of reference values of regional myocardial perfusion. Serial venous blood samples for residual 11C activity of 30 and 60 min after injection were less than 1% of the myocardial 11C concentration demonstrating a stable 11C bond to the human albumin microspheres. Regional myocardial perfusion calculated by this technique correlated well with values obtained with reference microspheres (r = .97) over a range of 0.2 to 3.5 ml/min/g. Correction for wall thickness improved the slope of the regression equation from y = 0.71 x -0.03 to y = 0.88 X -0.05. Thus, 11C human albumin microspheres are stable radiochemically and can be used as a quantitative measure of regional myocardial perfusion.
Protection of hypoxic myocardium by intracoronary administration of verapamil in open-chest dogs.
Authors: Mori H , Nagata M , Miyazaki T , Sakurai K , Ogawa S , Hattori S , Takahashi M , Nakamura Y
Published: June 2011

Hypoxic perfusion of the regional myocardium was performed in 34 open-chest dogs. In eight dogs in which the myocardium was perfused with original hypoxic Krebs-Henseleit (K-H) solution for 5 min (group I) there was a marked decrease in adenosine triphosphate content (2.03 +/- 0.44 mumol/g) and an increase in lactate content (8.65 +/- 2.26 mumol/g). In myocardium of nine dogs (group II) perfused with verapamil-containing (1.3 mg/dl) K-H solution and in that of nine dogs (group III) receiving Ca2+-free solution, the degrees of reduction in adenosine triphosphate (2.99 +/- 0.73 and 3.25 +/- 0.48 mumol/g, respectively) and of lactate accumulation (5.16 +/- 0.59 and 4.79 +/- 1.02 mumol/g, respectively) at 5 min were significantly less than in group I. Absence of statistically significant differences in hemodynamic parameters among these three groups indicates that the metabolic preservation in group II probably resulted from a direct effect of verapamil on the regional myocardium related to Ca2+ metabolism. However, metabolic data in four dogs of group I and four dogs of group III killed at 40 sec of perfusion, in conjunction with results of the analysis of regional contraction, revealed that the time courses of segmental shortening in the three groups did not account for the metabolic differences among them.
Effects of the site and timing of atrioventricular nodal input on atrioventricular conduction in the isolated perfused rabbit heart.
Authors: Mazgalev T , Dreifus L S , Ininuma H , Michelson E L
Published: June 2011

Programmed stimulation was used to study patterns of atrioventricular nodal propagation in an isolated rabbit heart preparation. Stimulation was done at the two major atrioventricular nodal input regions, the crista terminalis and interatrial septum, by use of various sequencing protocols. The influence of stimulation input interactions on atrioventricular nodal propagation was then evaluated with the use of simultaneous extracellular and intracellular recordings from the various regions of the atrioventricular node and His bundle. Activation of the atrioventricular node occurred predominantly via the stimulated input site, although perinodal conduction to the opposite input also occurred and could modify the atrioventricular conduction pattern. Engagement patterns of both AN and N fibers were dependent on the sequence of activation at the major input sites, and similar conduction times to the His bundle were often associated with different local activation times, depending on the site of premature stimulation. Conversely, if premature stimulation was timed to produce constant local activation times but the input site varied, then the time to His bundle activation could also vary. Atrioventricular nodal functional and effective refractory periods and conduction patterns were dependent on both the timing and pattern of engagement at the principal inputs to the atrioventricular node as well as the subsequent organization of activation of the various regions of the atrioventricular node. Furthermore, depending on the sequence of stimulation at the crista terminalis and interatrial septum, activation patterns were either organized or inhomogeneous in the AN and N regions of the atrioventricular node, consequently influencing the H-H interval, and in some instances resulting in conduction block to the His bundle. It is concluded that the relative timing of activation at the principal input regions of the atrioventricular node is critical to patterns of atrioventricular nodal propagation and subsequent conduction to the His bundle. Our results emphasize the complexity of atrioventricular nodal propagation during premature stimulation.
Global and regional left ventricular function and tomographic radionuclide perfusion: the Western Washington Intracoronary Streptokinase In Myocardial Infarction Trial.
Authors: Ritchie J L , Davis K B , Williams D L , Caldwell J , Kennedy J W
Published: June 2011

The Western Washington Intracoronary Streptokinase In Myocardial Infarction Trial enrolled 250 patients with acute myocardial infarction. After the coronary angiographic diagnosis of thrombosis, patients were randomly assigned to receive either conventional therapy with heparin or intracoronary streptokinase followed by heparin. Of the 232 patients who survived at least 60 days, 207 (89%) underwent radionuclide ventriculographic determination of global and regional ejection fraction at a single institution at 62 +/- 35 days after infarction. In the first 100 patients, infarct size was also determined by quantitative single-photon emission tomographic imaging with thallium-201 (201Tl) and expressed as a percentage of the left ventricle with a perfusion defect. Overall, global ejection fraction did not differ between patients treated with streptokinase (45.9 +/- 13.9%; n = 115) and control patients (46.1 +/- 14.4%; n = 92, p = NS). Similarly, the regional posterolateral, inferior, and anteroseptal ejection fraction did not differ between the two groups. Infarct size as measured by 201Tl tomography was 19.4 +/- 12.8% (n = 52) of the left ventricle for the streptokinase group and 19.6 +/- 11.8% (n = 48; p = NS) for the control group. When patients were compared within groups by electrocardiographic location of infarction, time to treatment, or the presence or absence of vessel opening, there were no significant differences between streptokinase and control patients. Statistical inclusion of the 18 patients who died early and were unavailable for study also failed to modify the results, except for a possible reduction in inferior infarct size as measured by 201Tl tomography.(ABSTRACT TRUNCATED AT 250 WORDS)
Systemic venous and pulmonary arterial flow patterns after Fontan's procedure for tricuspid atresia or single ventricle.
Authors: DiSessa T G , Child J S , Perloff J K , Wu L , Williams R G , Laks H , Friedman W F
Published: June 2011

Despite increasing use of Fontan or modified Fontan repairs, the comparative hemodynamic efficacy of different types of connections are unresolved. Accordingly, we undertook a prospective study designed to determine postoperative flow patterns after Fontan's operation. Seven subjects had tricuspid atresia and eight had single ventricle. Ages ranged from 5 to 38 years (mean 16.4). Ten subjects had nonvalved right atrial-to-pulmonary arterial connection, and four had nonvalved right atrial-to-right ventricular communication. A valved conduit established continuity between the right atrium and right ventricle in one subject. Doppler flow profiles were recorded in the pulmonary artery and in the superior and inferior venae cavae of each. A reference electrocardiogram was used for timing purposes. In 14 patients, forward flow in the pulmonary artery was biphasic. Flow began at the end of the T wave (early ventricular diastole), peaked at or before the P wave (atrial systole), and returned to baseline by the peak of the R wave. Forward flow recommenced at the peak of the R wave (ventricular systole) and returned to baseline at the end of the T wave. Flow in the superior vena cava varied, and could not be recorded in three subjects. Between the end of the P wave and peak of the R wave (atrial systole) flow was reversed in eight, absent in three, and forward in one patient. Forward flow occurred between the peak of the R wave and the end of the T wave and was either continuous or biphasic. Fourteen patients had adequate studies of inferior vena cava flow; reversed flow during atrial systole occurred in 10 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Normalization of plasma lipoprotein concentrations in patients with type II hyperlipoproteinemia by combined use of neomycin and niacin.
Authors: Hoeg J M , Maher M B , Bou E , Zech L A , Bailey K R , Gregg R E , Sprecher D L , Susser J K , Pikus A M , Brewer H B
Published: June 2011

The oral administration of neomycin or niacin as single-drug therapy can significantly lower total and low-density lipoprotein cholesterol concentrations in patients with type II hyperlipoproteinemia. However, in the majority of patients treated with one of these drugs as sole therapy plasma lipid and lipoprotein concentrations do not normalize. The effect of combined neomycin (2 g/day) and niacin (3 g/day) treatment on the plasma lipoprotein concentrations was determined in 25 type II hyperlipoproteinemic patients in a double-blind, randomized, placebo-controlled, crossover clinical trial. Treatment with neomycin was well tolerated by all 25 study patients and significantly reduced total and low-density lipoprotein cholesterol concentrations by 23% and 29%, respectively (p less than .05). In contrast to the well-tolerated neomycin regimen, 11 patients (44%) were unable to continue niacin treatment because of adverse side effects. In the 14 patients treated with both neomycin and niacin, niacin further lowered the concentrations of total and low-density lipoprotein cholesterol by 18% and 25%, respectively, and increased high-density lipoprotein cholesterol by 32% (p less than .05) compared with that in the patients receiving neomycin plus niacin placebo. Compared with diet-only therapy, combined treatment with neomycin plus niacin reduced the total plasma cholesterol concentration by 36%, low-density lipoprotein cholesterol by 45%, and the low-density lipoprotein/high-density lipoprotein ratio by 46% and it increased plasma high-density lipoprotein concentrations by 24% (p less than .001). During the study, 80% of all the study patients and 92% of the patients who complied with the combined regimen normalized their total and low-density lipoprotein concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Hemodynamic and clinical limitations of long-term inotropic therapy with amrinone in patients with severe chronic heart failure.
Authors: Packer M , Medina N , Yushak M
Published: June 2011

To determine the hemodynamic and clinical effects of long-term positive inotropic stimulation on the myocardium, we treated 31 patients with severe chronic heart failure with oral amrinone (600 mg daily) and performed invasive hemodynamic studies during short- and long-term treatment with the drug. Stroke volume and stroke work indexes increased markedly during the first 48 hr of therapy (p less than .01) but returned to pretreatment values after 2 to 10 weeks; upon drug withdrawal, both variables deteriorated rapidly to values significantly lower than those observed before treatment with amrinone (p less than .01), despite similar values for left ventricular filling pressure, mean arterial pressure, and systemic vascular resistance. This pattern of response indicated that progression of the underlying heart disease had occurred during treatment with amrinone and contributed importantly to its failure to produce long-term benefits. Progression of left ventricular dysfunction was associated with a progressive increase in heart rate and plasma renin activity and a decline in serum sodium concentration. Clinically, amrinone therapy was complicated by sustained symptomatic ventricular tachycardia in four patients, worsening myocardial ischemia in four patients, and worsening congestive heart failure in eight patients, all of whom had been stable before entry into the study; only three of the 31 patients improved clinically. Ten patients died during the first 2 weeks of treatment, and 16 (52%) were dead within 3 months, a mortality rate twice as great as that seen during comparable trials with vasodilating drugs. Although noncardiac adverse effects were frequent, they were not the primary reason for drug failure. In conclusion, long-term therapy with amrinone may accelerate progression of left ventricular dysfunction, exacerbate myocardial ischemia, and provoke life-threatening ventricular tachyarrhythmias, thereby shortening survival in patients with severe chronic heart failure. Prolonged administration of inotropic drugs may achieve short-term gains at the expense of long-term detrimental effects on the myocardium.
Quantitation of size of relative myocardial perfusion defect by single-photon emission computed tomography.
Authors: Caldwell J H , Williams D L , Harp G D , Stratton J R , Ritchie J L
Published: June 2011

The purpose of this study was to validate a semiautomatic method for quantitating the size of relative myocardial perfusion defects from single-photon emission computed tomographic (SPECT) images. We compared the size of the image defect in vivo, expressed as percent of involved left ventricle, as determined by this method with the anatomic size of the defect in vitro in 19 dogs. To test the method under optimal conditions, we first labeled the left ventricular myocardium in nine dogs by left atrial injection of 99mTc-labeled macroaggregated albumin particles after acute occlusion of one coronary artery. The "defect volume" was defined as the volume of the left ventricular myocardium for which counts fell 2 or more SDs below the distribution of counts in the myocardium supplied by a normal coronary artery in a series of animals. The relative in vivo defect volume by SPECT occupied 26.46 +/- 12.7% of the left ventricular volume (mean +/- SD), compared with a relative defect size in vitro of 33.3 +/- 13.7% (p = NS) of left ventricular volume as determined by well counting of myocardial samples. There was a close correlation between the two measurements (r = .92). However, myocardial relative defect volumes involving less than 5% of myocardium were not identified by SPECT. The defect volume weighted for the relative reduction in flow within the defect zone or the relative "reduced perfusion volume" was also determined. The correlation between the estimates by SPECT and those made in vitro for relative reduced perfusion volume was also high (r = .94).(ABSTRACT TRUNCATED AT 250 WORDS)
Determinants of survival in patients with congestive cardiomyopathy: quantitative morphologic findings and left ventricular hemodynamics.
Authors: Schwarz F , Mall G , Zebe H , Schmitzer E , Manthey J , Scheurlen H , Kübler W
Published: June 2011

We analyzed data from 68 consecutive patients with congestive cardiomyopathy to evaluate the prognostic significance of quantitative morphologic findings in left ventricular myocardium as compared with the prognostic significance of left ventricular hemodynamics. Left ventricular endomyocardial biopsy specimens were obtained from all patients during diagnostic heart catheterization. Myocardial fiber diameter, volume fraction of interstitial fibrosis, and intracellular volume fraction of myofibrils were determined by light-microscopic morphometry. All patients had normal coronary arteriograms, but reduced left ventricular ejection fractions. There were 23 deaths during a mean follow-up period of 1124 days. Multivariate regression analysis (Cox model) revealed that left ventricular ejection fraction (p less than .00001) and left ventricular systolic pressure (p less than .01), but not morphometric findings in biopsy specimens, were independent predictors of cardiac death. Thus, morphologic findings in the left ventricular myocardium do not contribute significantly to the prognostic evaluation in patients with congestive cardiomyopathy studied by hemodynamic and angiographic methods.
Quantitative assessment of right and left ventricular growth in the human fetal heart: a pathoanatomic study.
Authors: St John Sutton M G , Raichlen J S , Reichek N , Huff D S
Published: June 2011

We quantitated the growth patterns of the normal fetal heart and the right and left ventricles from postmortem hearts obtained from 55 spontaneously aborted human fetuses from the completion of cardiogenesis to term. Fetal gestational age was assessed by menstrual history of the mother, crown-rump length, head circumference, and body weight and ranged from 8 to 40 weeks. Each heart was perfused and fixed at constant pressure and dissected to obtain right and left ventricular free wall, left ventricular, and total heart weights. Right and left ventricular free wall thicknesses were measured and the respective surface areas were calculated. The changes in each of these parameters with gestational age were examined by regression analysis. Total heart and right and left ventricular wall weights increased linearly with body weight, but exponentially with head circumference, crown-rump length, and menstrual history. Right and left ventricular free wall weights were similar throughout gestation and the percent that each contributed to total heart weight were constant at 29 +/- 2% and 30 +/- 2%, respectively. Right and left ventricular wall thicknesses did not differ significantly, increasing linearly with menstrual age, crown-rump length, head circumference, and body weight from 8 to 40 weeks. The surface areas of the right and left ventricular free walls that we used as an index of changing ventricular architecture were indistinguishable throughout the period of gestation studied.(ABSTRACT TRUNCATED AT 250 WORDS)