bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of regional myocardial perfusion and mass by subselective hydrogen infusion and washout techniques: a validation study.
Authors: Grines C L , Mancini G B , McGillem M J , Gallagher K P , Vogel R A
Published: June 2011

A technique was developed for measuring regional myocardial perfusion by intracoronary infusions of hydrogen (H2)-saturated saline. H2 concentration was detected during washout in the pulmonary artery by means of the voltage response of a platinum-tipped electrode. Regional myocardial perfusion was calculated from the H2 exponential desaturation curve according to the Kety-Schmidt principle. In 16 anesthetized open-chest dogs, validation of this technique was performed at baseline, reduced (stenosis), and hyperemic (dipyridamole) flow states by means of the radionuclide-labeled microsphere reference withdrawal technique. There was an excellent quadratic correlation between microsphere and H2 washout techniques (range 0.11 to 3.15 ml/min/g) (n = 33, r = .92, y = -0.12x2 + 0.89x + 0.20, SEE = 0.20 ml/min/g; p less than .0001). Hyperemic regional myocardial perfusion was underestimated by H2 washout and severely ischemic regional myocardial perfusion was overestimated. When regional myocardial perfusion values greater than twice normal were excluded, a strong linear correlation was present between H2 and microsphere measurements (n = 27, r = .89, y = 0.76x + 0.22, SEE = 0.18 ml/min/g; p less than .0001). The H2 washout method was further tested in 18 additional open chest dogs for calculations of the mass of an arterial perfusion bed according to the principle that the mass of the bed (g) equals coronary blood flow (ml/min) divided by regional myocardial perfusion (ml/min/g).(ABSTRACT TRUNCATED AT 250 WORDS)
Cine magnetic resonance imaging after surgical repair in patients with transposition of the great arteries.
Authors: Chung K J , Simpson I A , Glass R F , Sahn D J , Hesselink J R
Published: June 2011

Cine magnetic resonance imaging (MRI) was used for postoperative evaluation of eight patients who underwent intra-atrial baffle procedure for surgical repair of D-transposition of the great arteries (D-TGA). Their ages ranged from 9 months to 8 years. Younger patients were sedated with chloral hydrate (80 to 100 mg/kg) orally. MRI was performed with use of a General Electric Signa system operating at a field strength of 1.5 tesla. A body or head coil was used depending on the size of the patient. Images were obtained by use of a technique of gradient-recalled acquisition in steady state (GRASS) that utilizes a low flip angle and shorter repetition and echo times. Five patients had widely patent venae cavae and three had superior vena caval obstruction at the junction of the right atrium with a dilated azygos vein. There was no evidence of pulmonary venous obstruction in any of the patients. Right ventricular function was assessed in four patients and their ejection fractions ranged from 58% to 81%. Tricuspid and mitral regurgitation were observed in three and two patients, respectively. Both right and left ventricular outflow tracts were well visualized and showed no evidence of obstruction. Cine MRI is an entirely noninvasive, nonionizing, and safe procedure in young patients and appears to be a valuable alternative method for evaluating patients after surgical repair of D-TGA. With advancing technologies and an accumulation of experience with cine MRI, it appears that this new technique will play an important role in patient care for children with congenital heart disease.
Quantitative cineangiographic analysis of ventricular volume and mass in patients with single ventricle: relation to ventricular morphologies.
Authors: Sano T , Ogawa M , Yabuuchi H , Matsuda H , Nakano S , Shimazaki Y , Taniguchi K , Arisawa J , Hirose H , Kawashima Y
Published: June 2011

With the use of biplane selective ventriculography, the ventricular volume, ejection fraction, and ventricular mass were evaluated in 28 patients with a single ventricle, and those with the left ventricular type (LV type, 12 patients) and right ventricular type (RV type, 16 patients) were compared. There were no significant differences in terms of age, hemoglobin, systemic oxygen saturation, or pulmonary-to-systemic flow ratio in the two groups. No patients with atrioventricular valve regurgitation were included. The ventricular cavity volume was calculated by the area-length method. The ventricular mass volume was determined as the shell volume created by subtracting the ventricular cavity volume from the total ventricular volume calculated by adding the free wall thickness to the chamber dimensions. The ventricular mass volume was converted to mass by multiplying by the gravity of the heart muscle. There was no significant difference between patients with the LV type and RV type of single ventricle with respect to the end-diastolic ventricular volume (188 +/- 53 and 179 +/- 61 ml/m2 in LV and RV types, respectively), end-systolic volume (88 +/- 31 and 84 +/- 27 ml/m2), or ejection fraction (0.54 +/- 0.06 and 0.52 +/- 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)
Sequential thallium-201 myocardial perfusion studies after successful percutaneous transluminal coronary artery angioplasty: delayed resolution of exercise-induced scintigraphic abnormalities.
Authors: Manyari D E , Knudtson M , Kloiber R , Roth D
Published: June 2011

To characterize the sequential changes of myocardial perfusion scintigraphy in patients with coronary artery disease (CAD) after complete revascularization, 43 patients underwent exercise thallium-201 (201Tl) myocardial perfusion scintigraphy before and at 9 +/- 5 days, 3.3 +/- 0.6, and 6.8 +/- 1.2 months after percutaneous transluminal coronary angioplasty (PTCA). Only patients with single-vessel CAD, without previous myocardial infarction, and without evidence of restenosis at 6 to 9 months after PTCA were included. Perfusion scans were analyzed blindly with the use of a new quantitative method to define regional myocardial perfusion in the topographic distribution of each coronary artery, which was shown to be reproducible (r = .94 or higher and SEE of 7% or less, between repeated measures by one and two operators). At 4 to 18 days after PTCA, the mean treadmill walking time increased by 123 +/- 42 sec, mean exercise-induced ST segment depression decreased by 0.6 +/- 0.3 mm, group maximal heart rate increased by 20 +/- 9 beats/min, and group systolic blood pressure at peak exercise increased by 24 +/- 10 mm Hg, compared with pre-PTCA values (p less than .001). However, no group differences were noted in these variables between the three post-PTCA stages. Myocardial perfusion in the distribution of the affected (dilated) coronary artery, on the other hand, improved progressively. In the 45 degree left anterior oblique view for instance, myocardial perfusion increased at 9 days after PTCA (from 68 +/- 24% before PTCA to 91 +/- 9%, p less than .001) and at 3.3 months after PTCA (101 +/- 8%, p less than .05 vs 9 days after PTCA), but no further significant changes were seen at 6.8 months after PTCA (102 +/- 8%). Similar changes were noted in the other two views. No relationship between minor complications during PTCA and delayed improvement on the 201Tl was observed. Myocardial ischemia was diagnosed in 12 of the 43 scans recorded a few days after PTCA, but in none recorded at later stages. We conclude that 201Tl scans after PTCA often show delayed improvement and therefore, an abnormal myocardial perfusion scan soon after PTCA does not necessarily reflect residual coronary stenosis or recurrence.
The contribution of magnetic resonance imaging to the evaluation of intracardiac tumors diagnosed by echocardiography.
Authors: Freedberg R S , Kronzon I , Rumancik W M , Liebeskind D
Published: June 2011

MAgnetic resonance (MR) imaging was performed in 14 patients with intracavitary cardiac tumors diagnosed by echocardiography. Except in the patients whose echocardiograms were diagnostic of atrial myxomas, this modality contributed important additional anatomic information regarding the tumor's relationship to the normal intracardiac structures and/or its extension to the adjacent vascular and mediastinal structures. The MR findings correlated extremely well with the findings in all 12 patients who underwent surgical exploration or postmortem examination, and in the other two patients, MR guided the decision to obtain transvenous biopsy samples of their right heart masses.
Atrial natriuretic peptide in congestive heart failure in the dog: plasma levels, cyclic guanosine monophosphate, ultrastructure of atrial myoendocrine cells, and hemodynamic, hormonal, and renal effects.
Authors: Riegger G A , Elsner D , Kromer E P , Daffner C , Forssmann W G , Muders F , Pascher E W , Kochsiek K
Published: June 2011

In an animal preparation of congestive heart failure in the dog, during the development of cardiac failure due to rapid right ventricular pacing we observed significant decreases in cardiac output and arterial pressure and increases in pulmonary arterial and right atrial pressure. We also observed a related increase in right atrial pressure and increases in plasma levels of atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (c-GMP). Ultrastructure changes in the atrial myoendocrine cells indicated extreme stimulation of the secretory apparatus of ANP. The response of hemodynamic, renal, and hormonal variables was investigated after incremental infusions (0.01, 0.03, 0.1, 0.3, and 0.06 microgram/kg/min) of exogenous ANP. In healthy animals ANP significantly decreased mean arterial pressure, cardiac output, stroke volume, and right atrial pressure without changing heart rate or peripheral vascular resistance. As expected, we found a striking increase in urine flow and urinary excretion of sodium, chloride, magnesium and calcium and a smaller increase in potassium excretion. ANP suppressed renin secretion, and increased renal plasma flow, glomerular filtration rate, and filtration fraction. In dogs with heart failure ANP caused a small reduction in mean arterial pressure. No effect was seen on other hemodynamic variables or plasma renin concentration. The excretory effects on the kidneys were completely absent, and smaller increases in glomerular filtration rate and filtration fraction were observed. We found no difference between healthy dogs and animals with heart failure with respect to the secretion of c-GMP during ANP infusions in relation to the plasma levels of ANP. This suggests an intracellular defect that prevents the mediation of the hormonal signal into biological action in the presence of heart failure.
Does normal pump function belie muscle dysfunction in patients with chronic severe mitral regurgitation?
Authors: Wisenbaugh T
Published: June 2011

Left ventricular cineangiography and micromanometry were performed simultaneously in 27 patients with chronic severe mitral regurgitation (MR group) and in 23 normal subjects (NL group). Stress (sigma) and volume (V) were computed frame by frame. Measurements were repeated after pharmacologic load manipulation in subsets of MR (n = 10) and NL (n = 11) groups. An inverse relationship (r = -.90) between EFc (ejection fraction determined from a common preload) and sigma es (afterload) was observed for the NL group. For the MR group, 10 of 14 with EFs less than 0.60 and four of 13 with EFs greater than 0.60 had muscle dysfunction, falling below the 95% prediction band of the normal EFc-sigma es relationship. Maximum myocardial stiffness (maxEN) determined from the end-systolic stress-strain relationship of Mirsky, sigma es = maxEN.gamma.loge(Ves/Vo), was 1398 +/- 716 in the MR (n = 10) vs 1165 +/- 394 in the NL group (n = 11, NS). EF was 0.62 +/- 0.13 in the MR and 0.65 +/- 0.08 in the NL group. Mitral valve surgery was performed on 19 of the patients with MR. All survived and all but one were symptomatically improved; that patient required reoperation in the early postoperative period because of transverse midventricular disruption. Thus, contractile function as assessed by stress-strain and EFc-afterload relationships is frequently normal in individuals with MR when EF is normal. When EF is depressed, contractile function as assessed by EFc-afterload relationships is frequently depressed, but this does not preclude a satisfactory surgical result.
Degree of revascularization in patients with multivessel coronary disease: a report from the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry.
Authors: Reeder G S , Holmes D R , Detre K , Costigan T , Kelsey S F
Published: June 2011

There is controversy regarding the application of angioplasty to patients with multivessel disease in whom all significant stenoses are not dilated. We analyzed the outcomes of 286 patients with multivessel disease and prior successful angioplasty at a mean follow-up duration of 26.2 months. End points analyzed included death, myocardial infarction, late revascularization, and angina pectoris. After successful angioplasty, 127 patients had no residual stenoses of 70% or greater (group 1) and 159 patients had one or more residual stenoses of 70% or greater (group 2). Because there were significant differences in baseline risk factors between the two groups, a logistic regression model was used to make the necessary adjustments in the analysis. Adjusted estimates of the risk of death, death/myocardial infarction, or presence of angina pectoris did not differ between the two groups. Group 2 patients, however, had more coronary artery bypass surgery during follow-up, while those in group 1 had more second PTCA procedures. Results suggest that angioplasty can be safely applied to patients with multivessel disease, even when all significant stenoses are not dilated.
Serial immunologic identification of lymphocyte subsets in murine coxsackievirus B3 myocarditis: different kinetics and significance of lymphocyte subsets in the heart and in peripheral blood.
Authors: Kishimoto C , Misaki T , Crumpacker C S , Abelmann W H
Published: June 2011

To elucidate possible immune mechanisms in the pathogenesis of myocarditis, we examined, by immunofluorescence techniques, the serial changes in lymphocyte subsets in the heart, spleen, and peripheral blood of C3H/He mice inoculated coxsackievirus B3 (experiment I). B cells were identified by staining with fluorescein isothiocyanate-labeled rabbit antimouse immunoglobulin. T cell subsets were demonstrated with rat anti-Thy 1.2, anti-Lyt 1, anti-Lyt 2, and anti-L3T4 monoclonal antibodies, respectively, plus fluorescein isothiocyanate-labeled antimouse immunoglobin. The percent of Thy 1.2+, Lyt 1+, and L3T4+ cells was decreased in the peripheral blood on days 3, 7, and 14. B cells were increased on day 3. In contrast, Thy 1.2+ (pan T) or Lyt 1+ cells appeared to occupy the major portion of the myocardium on days 7 and 14, when myocarditis was most severe, while B cells were sparse. For confirmation, serial immunohistologic studies (immunoperoxidase staining) of the hearts of C3H/He mice with coxsackievirus B3 myocarditis were performed (experiment II). Most of the stained cells in the heart were Thy 1.2, Lyt 1, and Lyt 2 positive on days 7 and 14. Thus, independent methods demonstrate that specific antigenic markers on lymphocytes at the site of inflammation in the acute stage of viral myocarditis differ from those on corresponding peripheral lymphocytes, and suggest the possible involvement of Thy 1.2+ (pan T) cells, mainly the Lyt 1+ and Lyt 2+ subsets (immature T cells), in the development of myocarditis in this preparation.
Time domain echo pattern evaluations from normal and atherosclerotic arterial walls: a study in vitro.
Authors: Picano E , Landini L , Lattanzi F , Salvadori M , Benassi A , L'Abbate A
Published: June 2011

The aim of this study in vitro of human fresh specimens was to quantitatively evaluate the contribution of the aqueous phase-intima interface (the first 400 msec of the reflected signal) in normal and atherosclerotic arterial walls. Seventy-five samples were studied, 15 normal, 15 fatty, 15 fibrofatty, 15 fibrous, and 15 calcific. A broadband transducer (4 to 14 MHz) was used. The aqueous phase-intima reflection (expressed in dB, mean +/- SD) was lowest in the fatty plaques (-35.3 +/- 2.5), differing in a highly significant way from that in all other groups: normal (-13.2 +/- 8.8), fibrofatty (-20.4 +/- 8.3), fibrous (-13.0 +/- 9.7), calcific (-5.9 +/- 3.4). The echo coming from the intima-media transition was of relatively low amplitude in normal and in fatty samples; typically, strong reflections from the intima-media transitions were present in the other pathologic subsets. In conclusion, the time domain echo pattern of the arterial wall may provide a useful clue to the structure of the plaque.
Electrogram patterns predicting successful catheter ablation of ventricular tachycardia.
Authors: Fitzgerald D M , Friday K J , Wah J A , Lazzara R , Jackman W M
Published: June 2011

Ventricular tachycardia in patients with remote myocardial infarction is thought to be due to reentry. To improve the efficacy of catheter ablation, we sought to identify electrograms identifying essential components of the reentrant circuit. In this study we compared the efficacy of shocks delivered at sites of early ventricular activation during tachycardia (presumably exit sites from the reentrant circuit) with that of shocks delivered at sites recording mid-diastolic potentials that were not continuous with the main ventricular potential recorded during the QRS complex, but that always remained associated with the tachycardia during initiation, termination, and resetting with extrastimuli (presumably activation of a segment of the slowly conducting region of the reentrant circuit). A total of 20 attempts was made to ablate 14 monomorphic ventricular tachycardias in 10 patients with remote myocardial infarction with use of one to five shocks of 50 to 370 J (200 J in 70%). All seven tachycardias in which isolated mid-diastolic potentials were targeted were successfully ablated, although one required a second attempt. Twelve attempts were made to ablate seven tachycardias by delivering shocks at sites of early activation during tachycardia when mid-diastolic potentials were not identified. Only three attempts (25%) were successful. Activation preceded the QRS complex by 60, 85, and 120 msec in the three successful attempts and by 20 to 110 msec (median 55 msec) in the nine unsuccessful attempts. For the total 20 attempts, there was no significant difference between successful and nonsuccessful ablation in the number of shocks or total energy delivered.(ABSTRACT TRUNCATED AT 250 WORDS)
Clinical outcome 5 years after attempted percutaneous transluminal coronary angioplasty in 427 patients.
Authors: Talley J D , Hurst J W , King S B , Douglas J S , Roubin G S , Gruentzig A R , Anderson H V , Weintraub W S
Published: June 2011

This study was performed to define the 5 year clinical status of 427 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) in 1981. Their mean age was 54 +/- 10 years (+/- 1 SD). Sixty-one percent had unstable angina, 23% had prior myocardial infarction, 86% had one-vessel disease, and 92% had normal left ventricular function. Sixty-seven percent of patients had left anterior descending artery stenosis. Angiographic success was achieved in 84% of patients. Coronary bypass surgery was required in 9.6% of patients, in 5.9% as an emergency procedure. There were no in-hospital deaths. Follow-up at 5 years was 100% complete. There were 15 late deaths (96.3 +/- 1.0% survival), including seven of cardiac cause (98.1 +/- 0.7% cardiac survival). Myocardial infarction occurred in 24 patients (94% freedom from myocardial infarction), coronary bypass surgery was required in 63 (84% freedom from bypass surgery), and 365 patients (85%) were asymptomatic at follow-up. At 5 years, 83 patients (20%) had required an additional PTCA. Unstable angina pectoris and proximal left anterior descending coronary artery stenoses were present in 162 patients. The overall survival and cardiac survival in this subset was 94.4 +/- 1.8% and 98.1 +/- 1.1%, respectively. The excellent survival and low event rates over 5 years in this population support the concept that PTCA is safe and effective for patients with symptomatic angina pectoris, single-vessel disease, and normal left ventricular function.
Biochemical determinants of clearance of tissue-type plasminogen activator from the circulation.
Authors: Lucore C L , Fry E T , Nachowiak D A , Sobel B E
Published: June 2011

Biochemical modification of tissue-type plasminogen activator (t-PA) designed to alter pharmacokinetics and pharmacodynamics offers promise for development of pharmaceuticals particularly suitable for treatment of specific disorders and for induction of coronary thrombolysis by intramuscular as well as intravenous administration. Accordingly, to identify biochemical determinants of clearance of t-PA from the circulation, we injected rabbits intravenously with three different preparations of t-PA synthesized from the same human gene and expressed in Chinese hamster ovary cells cultured under disparate conditions. Influences of glycosylation on clearance were defined by experiments with enzymatically treated t-PA in which clearance was assessed with concomitant administration of selected neoglycoproteins that compete with t-PA for specific glycoprotein receptors. The role of an intact active catalytic site, as reflected by differences in clearance with and without prior treatment of t-PA with the protease inhibitor PPACK, was defined also. Results indicate that clearance is altered by inhibition of the active site and that the nature and extent of glycosylation--not evident simply by analysis of peptide structure--influence clearance as well. These findings suggest that mannose/N-acetylglucosamine-specific glycoprotein receptors expressed on hepatic reticuloendothelial cells participate in clearance of t-PA from the circulation but that galactose-specific glycoprotein receptors probably do not. The observations may explain differences in clearance seen with different preparations of t-PA that have been seen in clinical pilot studies and may identify biochemical determinants of clearance amenable to modification for development of agents with potentially desirable, specific biological properties.
The effects of a critical stenosis on myocardial blood flow, ventricular function, and infarct size after coronary reperfusion.
Authors: Lefkowitz C A , Pace D P , Gallagher K P , Buda A J
Published: June 2011

Immediate percutaneous transluminal coronary angioplasty has been advocated for patients with a residual stenosis after coronary thrombolysis because of the possibility that the residual stenosis may restrict reflow and thereby increase infarct size. Because there are few experimental data bearing on this issue, we measured left ventricular function, myocardial blood flow, and infarct size in 20 anesthetized open-chest dogs during 2 hr of left circumflex occlusion and 4 hr of reperfusion. Ten animals were reperfused through a critical stenosis of the left circumflex artery (critical stenosis group) and the remaining 10 animals underwent full reperfusion without stenosis (control group). In both groups, a comparable degree of echocardiographic systolic wall thinning was present during occlusion and partial recovery of global and regional left ventricular function in the two groups. Subendocardial blood flow was decreased in the critical stenosis group relative to the control group at 5 min after reperfusion (0.52 +/- 0.16 ml/min/g in the critical stenosis group vs 1.55 +/- 0.32 ml/min/g in the control group, p less than .05) but not at 4 hr after reperfusion, when a reduced reflow response was seen in both groups. No differences in subepicardial blood flow were seen in the two groups of animals. Infarct size was slightly greater in the critical stenosis group than the control group, but this difference was not statistically significant (infarct/risk area ratio: 55.5 +/- 7.8% in the critical stenosis group vs 39.4 +/- 9.7% in the control group, p = .21). A close inverse exponential relationship was seen between infarct size/risk area ratio and subendocardial blood flow during occlusion (r = .89, p = .001). Two control animals had high levels of subendocardial collateral flow (greater than 0.2 ml/min/g); when these animals were excluded from analysis, differences in the infarct size/risk area ratio in the control and critical stenosis groups were less striking: (55.5 +/- 7.8% in the critical stenosis group vs 48.4 +/- 9.6% in the control group). Thus, the presence of a critical stenosis results in restriction of hyperemic blood flow to the subendocardium after reperfusion but does not influence infarct size or early left ventricular functional recovery.
Outpatient closure of the patent ductus arteriosus.
Authors: Wessel D L , Keane J F , Parness I , Lock J E
Published: June 2011

We have modified and applied to selected outpatients the transvenous approach to correction of patent ductus arteriosus (PDA) with the Rashkind PDA Occluder. Modifications included establishing the diagnosis and PDA anatomy before catheterization with echocardiography. The sedation/anesthetic regimen was altered to meet the needs with respect to transcatheter PDA closure rather than diagnostic cardiac catheterization. Anticoagulation was avoided. A strategy for management of pin entrapment in the foam was devised. Residual trans-PDA flow after umbrella placement was temporarily occluded with balloon-tipped catheters. These modifications were used in 23 consecutive patients with uncomplicated PDA. Closure was successful in each child. Nineteen of 23 patients were discharged on the day of the procedure. No serious complications were encountered.
Efficiency of energy transfer from pressure-volume area to external mechanical work increases with contractile state and decreases with afterload in the left ventricle of the anesthetized closed-chest dog.
Authors: Nozawa T , Yasumura Y , Futaki S , Tanaka N , Uenishi M , Suga H
Published: June 2011

We studied the effects of ventricular end-systolic elastance (Ees) and effective arterial elastance (Ea) on the efficiency of energy transfer from pressure-volume area (PVA) to external mechanical work (EW) in the left ventricle of anesthetized closed-chest dogs. PVA represents the total mechanical energy generated by ventricular contraction, which is an intermediate form of energy between oxygen consumption, the total energy input, and EW, the effective energy output. PVA and EW were determined from ventricular pressure and volume, which were continuously measured with a volumetric conductance catheter. Measurements of Ees were obtained by transiently increasing afterload by an inflation of a Fogarty catheter in the thoracic descending aorta. Ea was determined as the ratio of end-systolic pressure to stroke volume. The EW/PVA efficiency of a steady-state contraction increased from 55% to 64%, with a 58% increase in Ees after dobutamine. Ees, which was smaller than Ea before dobutamine, became nearly equal to Ea after dobutamine, maximizing EW for a given end-diastolic volume. EW/PVA efficiency decreased with an abrupt increase in afterload before and after dobutamine. The sensitivity of the decrease in the EW/PVA efficiency to an increase in end-systolic pressure was significantly less after than before dobutamine. We could account for all these changes in EW/PVA efficiency by the relative changes in Ees and Ea in the pressure-volume diagram.
The response to overdrive pacing of triggered atrial and ventricular arrhythmias in the canine heart.
Authors: Malfatto G , Rosen T S , Rosen M R
Published: June 2011

Although triggered activity has been identified in isolated atrial tissue with the use of cellular electrophysiologic techniques, there has been no identification of triggered atrial arrhythmias in situ. Moreover, it is unclear whether triggered rhythms of different causes and sites of origin in the heart exhibit uniform responses to pacing that might aid in their identification. We therefore studied arrhythmias induced by overdrive pacing in three canine preparations, and based the analysis of our results on guidelines derived from microelectrode studies. We studied ventricular tachycardias induced by ouabain or by anterior wall myocardial infarction and atrial (coronary sinus) arrhythmias induced by the infusion of epinephrine into the great cardiac vein. In the ouabain and postinfarction preparations, right ventricular epicardial pacing induced ventricular premature beats or tachycardias whose recovery intervals after cessation of pacing shortened and showed overdrive acceleration as pacing rate increased. The first postpacing beat displayed progressive fusion with the paced beats but transient entrainment could not be induced. In the coronary sinus, the recovery intervals of impulses induced by epinephrine and pacing decreased as the drive rate increased, and inducibility of the paced rhythms increased at faster drive rates. Thus, the recovery intervals of triggered activity induced in the coronary sinus are phenomenologically similar to those of infarct- and digitalis-induced triggered rhythms. This is the first demonstration of consistent behavior in response to pacing of diverse types of triggered activity. Considered in light of the failure to induce transient entrainment, the results emphasize the potential utility of pacing in clinical identification of triggered rhythms and their differentiation from reentry.
Frequency-dependent effects of quinidine on the relationship between action potential duration and refractoriness in the canine heart in situ.
Authors: Franz M R , Costard A
Published: June 2011

To determine the normal relationship in vivo between action potential duration (APD) and effective refractory period (ERP) over a large range of steady-state cycle lengths (CLs) and to determine how a sodium channel-blocking agent, quinidine, affects this relationship, we developed a new contact electrode technique for simultaneous measurements of monophasic action potentials and refractoriness at a single site in the beating heart in situ. Recordings were made from left ventricular epicardium in open-chest dogs during steady-state pacing at CLs from 220 to 600 msec both before and after therapeutic intravenous administration of quinidine. During baseline both APD at 90% repolarization (APD90) and ERP were linearly correlated to CL with nearly identical slopes: y = 0.24x CL + 83.0 (r = 1.0; p less than .0001) for APD90 and y = 0.22x CL + 82.3 (r = 1.0; p less than .0001) for ERP. Expressed in percent repolarization, ERP coincided with a repolarization level of 79% to 83%, with no appreciable influence of CL on this relationship. Quinidine increased APD90 by a small but significant amount (8 to 12 msec), which was independent of CL. In contrast, the effect on ERP of quinidine exhibited marked frequency dependence (p less than .0002), producing progressively greater ERP increase at shorter CLs, as compared with both baseline ERP and concomitant APD90. The duration by which ERP exceeded APD90 reached 44 +/- 14 msec at a CL of 220 msec.(ABSTRACT TRUNCATED AT 250 WORDS)
Correlation between echocardiographic endocardial surface mapping of abnormal wall motion and pathologic infarct size in autopsied hearts.
Authors: Wilkins G T , Southern J F , Choong C Y , Thomas J D , Fallon J T , Guyer D E , Weyman A E
Published: June 2011

We previously developed a cross-sectional echocardiographic technique for quantitatively mapping the endocardial surface of the left ventricle and on which regions of abnormal wall motion can be superimposed in their correct spatial distribution. This endocardial mapping technique (EMT) provides a measure of the left ventricular endocardial surface area (ESA in cm2), the area of abnormal wall motion (AWM in cm2), and the overall percent dysfunction (%AWM) as a measure of the functional "infarct size." To test this approach, we compared the EMT measurements with the actual endocardial surface area (in cm2) and pathologic infarct size (both percent infarct by volume and percent endocardial surface overlying infarct) measured at later autopsy in 20 adults (14 men, six women) ranging in age from 47 to 76 years (mean 64 +/- 9.6 years). The median interval from echocardiographic study to death was 19 days (range 1 to 269 days). Patients were divided into two groups based on the age of their infarcts at the time of death: (1) recent (infarct age less than 14 days; mean age 5.3 +/- 4.6 days) and (2) old (infarct age greater than 6 months; mean age 3.6 +/- 3 years). When the left ventricular endocardial surface area at autopsy was compared with the EMT-derived ESA, a close correlation was found (EMT area = 1.17 X autopsy area + 20.4; r = .94, p = .0001), with the systematic difference in the measurements accounted for by systolic arrest, loss of distending pressure, and specimen shrinkage. The echocardiographic measure of infarct size (%AWM) correlated well with the autopsy percent infarction by volume (%AWM = 1.1 X infarct volume + 5.5; r = .82, p = .0001). Similarly, a good correlation was found for the percent abnormal wall motion and the autopsy percent endocardial surface area overlying infarction (%AWM = 0.89 X infarct area - 0.9; r = .89, p = .0001). When the data were examined in relation to the age of the myocardial infarct, the echocardiographic %AWM appeared to overestimate the autopsy infarct size (by percent infarct volume) in the recent infarct group (n = 6), and underestimate the extent in the old infarct group (n = 13). The findings suggest that the EMT will provide a useful quantitative measure of left ventricular endocardial surface area and the extent of ischemic/infarct-related dysfunction.
Apparent finger systolic pressures during cooling in patients with Raynaud's syndrome.
Authors: Carter S A , Dean E , Kroeger E A
Published: June 2011

Despite considerable research, the mechanisms responsible for the vasospasm associated with Raynaud's syndrome are not well understood and there is no reliable diagnostic test. In the present studies, measurements of systolic pressure in locally cooled fingers were used to address these issues. We found that local cooling produced a marked decrease or loss of the apparent finger systolic pressure in patients with Raynaud's syndrome in whom a standardized vasoconstriction had been induced by body cooling. Abnormal responses were encountered in 109 of 125 patients with secondary Raynaud's syndrome, in 21 of 37 patients with primary Raynaud's disease or the syndrome of uncertain cause, and in two of 63 subjects without symptoms of Raynaud's. These data suggest a high accuracy of the test in patients with secondary Raynaud's syndrome and lower accuracy in those with disease of primary or uncertain cause. We studied responses of systolic pressures to alterations in body and local temperatures in fingers with and without low pressures secondary to proximal arterial obstruction. Our data show that although local cooling has a small independent effect that increases vascular tone: (1) sympathetic vasoconstriction induced by body cooling is necessary to produce vasospasm and often produces it without local cooling, (2) high local temperature (30 degrees C) protects from vasospasm, and (3) low finger blood pressure predisposes to it. Delayed opening of the vessels observed after sudden deflation of blood pressure cuffs suggests that abnormal responses of finger systolic pressure to cold represent combined effects of high vascular tone, delayed opening, and local blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
Development of the coronary arteries in the embryonic human heart.
Authors: Hutchins G M , Kessler-Hanna A , Moore G W
Published: June 2011

It is not known why the coronary arteries almost always originate only from the right and left aortic sinuses of Valsalva, since the structure and conditions appear to be the same for all six sinuses of the embryonic great arteries. We sought a possible mechanical explanation for the phenomenon by studying the development of the coronary vasculature in 351 staged, serially sectioned human embryos of Carnegie stages 9 through 23 from the Carnegie Embryological Collection. A plexus of blind epicardial capillaries appears on the heart in Carnegie stage 14 or 15 and acquires a coronary sinus connection in stage 15, 16, or 17. The connection of the proximal coronary arteries to the aorta does not appear until stage 18. We found no histologic features of the cardiac nerves or any other component of the tissues to account for the consistent origin of coronary arteries from the right and left aortic sinuses of Valsalva. However, serial section reconstructions showed that the two sinuses where coronary arteries develop acquire a positive transverse curvature and a negative longitudinal curvature, i.e., a catenoidal or saddle-shaped configuration, before the appearance of the coronary arteries. The four noncoronary sinuses also have a positive transverse curvature, but longitudinally, in contrast, they have a positive curvature or are straight. The results suggest that the coronary arteries originate from those sinuses of Valsalva where wall tension is increased by a catenoidal configuration.
Wideband external pulse recording during cuff deflation: a new technique for evaluation of the arterial pressure pulse and measurement of blood pressure.
Authors: Blank S G , West J E , Müller F B , Cody R J , Harshfield G A , Pecker M S , Laragh J H , Pickering T G
Published: June 2011

Analysis of the external brachial pulse recorded during standard blood pressure cuff deflation with use of a transducer with a wide frequency response has revealed a reproducible pattern with three distinct components that we have labeled K1, K2, and K3. K1 is a low-amplitude, low-frequency signal that is present with cuff pressures above systolic pressure. K2 is a triphasic signal appearing at systolic pressure and disappearing at diastolic pressure, which approximately corresponds to the audible Korotkoff sound. K3 appears with cuff pressure between systolic and diastolic pressure and continues to be present below diastolic pressure. Intra-arterial pressure recordings made with a high-fidelity Millar catheter-tip manometer revealed K2 and K3 analogs. K3 resembles the intra-arterial pressure waveform and when calibrated according to the pulse pressure, noninvasive dK3/dt determinations correlated well with intra-arterial dP/dt measurements. The appearance/disappearance property of K2 was designated as the "K2 algorithm" and represents a new, objective noninvasive method for measurement of blood pressure. The K2 algorithm compares favorably with intra-arterial measurements, is more accurate than the auscultatory technique, and may be especially useful in clinical situations in which the auscultatory technique does not work well.
Time course of regression of left ventricular hypertrophy after aortic valve replacement.
Authors: Monrad E S , Hess O M , Murakami T , Nonogi H , Corin W J , Krayenbuehl H P
Published: June 2011

To assess the time course and extent of regression of myocardial hypertrophy after removal of the inciting hemodynamic stress, 21 patients with either aortic stenosis or aortic insufficiency were studied preoperatively, after an intermediate period (1.6 +/- 0.5 years), and late (8.1 +/- 2.9 years) after aortic valve replacement, and results were compared with those in 11 control patients. After aortic valve replacement there was significant hemodynamic improvement, with a fall in the left ventricular end-diastolic volume index (164 +/- 73 to 105 +/- 35 ml/m2, p less than .01), a fall in left heart filling pressure (19 +/- 9 to 12 +/- 5 mm Hg, p less than .01), and maintenance of the cardiac index (3.3 +/- 0.8 to 3.5 +/- 0.8 liters/min/m2, NS) and left ventricular ejection fraction (60 +/- 13% to 64 +/- 10%, NS). By the late study the cardiac index (4.0 +/- 0.6 liters/min/m2, p less than .01) and left ventricular ejection fraction (66 +/- 15%, p less than .05) had further increased and were significantly greater than before surgery. For the group as a whole, the left ventricular muscle mass index fell 31% after surgery by the time of the intermediate postoperative study (174 +/- 38 vs 120 +/- 29 g/m2, p less than .01), and a further 13% from the intermediate to the late study (105 +/- 32 g/m2, p less than .05). At the preoperative study left ventricular muscle mass index was greatest in those patients with aortic insufficiency (191 +/- 36 g/m2), and greater in those with aortic stenosis (158 +/- 33 g/m2) than in control subjects (85 +/- 9 g/m2, p less than .05). At the intermediate postoperative study left ventricular muscle mass index remained significantly higher in both those with preoperative aortic insufficiency (128 +/- 29 g/m2) and those with stenosis (114 +/- 27 g/m2) than in the control subjects (p less than .01). By the time of the late postoperative study there were no longer any significant differences in left ventricular muscle mass index. Thus, the regression of myocardial hypertrophy is a process that occurs over many years after correction of the primary hemodynamic abnormality. As this process of myocardial remodeling occurs, continued improvement in cardiac function may occur, and the improvement occurring between the intermediate and late postoperative studies at a slight but constant afterload excess (inherent in the relative stenosis of the aortic prosthesis) suggests that the hypertrophied myocardium is operating at a reduced level compared with normal myocardium.
Combination therapy with diltiazem and nifedipine in patients with effort angina pectoris.
Authors: Toyosaki N , Toyo-oka T , Natsume T , Katsuki T , Tateishi T , Yaginuma T , Hosoda S
Published: June 2011

The antianginal effects of diltiazem and nifedipine alone and in combination were evaluated in a double-blind, randomized, placebo-controlled trial in 11 patients (nine men and two women, 57 +/- 8 years old) with stable effort angina. Each patient received placebo, 30 mg of diltiazem, 10 mg of nifedipine, and 30 mg of diltiazem plus 10 mg of nifedipine four times daily for 1 week each. Antianginal efficacy was assessed by means of a treadmill exercise test. The exercise tolerance time was significantly prolonged from 235.1 +/- 52 (placebo period) to 342.2 +/- 101 sec by diltiazem (p less than .01) and to 325.6 +/- 73 sec by nifedipine (p less than .01). The drug combination further prolonged exercise time to 451.1 +/- 103 sec, which was significantly longer than the interval attained with either diltiazem (p less than .01) or nifedipine (p less than .01) alone. The plasma concentration of diltiazem was unaffected by the addition of nifedipine, whereas the plasma nifedipine concentration was significantly increased from 34.8 +/- 11 to 106.4 +/- 37 ng/ml (p less than .001) by the concomitant administration of diltiazem. These data suggest that exercise tolerance in patients with effort angina is increased by the concomitant administration of diltiazem and nifedipine associated with an increase in the nifedipine plasma concentration.
Antianginal effects of intravenous nitroglycerin over 24 hours.
Authors: Zimrin D , Reichek N , Bogin K T , Aurigemma G , Douglas P , Berko B , Fung H L
Published: June 2011

To determine the constancy of hemodynamic and antianginal effects of the constant infusion of intravenous nitroglycerin (NTG) and their relationship to infusion rate and plasma NTG concentration, we administered maximal tolerated doses of intravenous NTG (range 10 to 120 micrograms/min, mean = 52 +/- 33 micrograms/min) and placebo to 10 patients with chronic stable angina for 25 hr each in a randomized, double-blind fashion. Sublingual NTG (0.4 mg) was given at 24.5 hr of infusion as a positive control. Bicycle exercise time (NIH protocol), blood pressure, heart rate, exercise ST response, and venous plasma NTG were determined before and at 1, 4, 8, 24, and 24.5 hr. Plasma NTG was linearly related to infusion rate, reached a steady state within 15 min and was unchanged over 24 hr (mean = 5.5 +/- 1.2 ng/ml). Mean plasma NTG clearance was 9.3 liters/min. However, during dose titration, patients demonstrated different relationships between plasma NTG and hemodynamic effects, with widely varying slopes and intercepts. Intravenous NTG produced a sustained reduction in blood pressure and a rise in heart rate at rest, and a reduction in blood pressure during submaximal exercise at as late as 24 hr, associated with reduced submaximal ST segment abnormality. In contrast, exercise tolerance to onset of angina showed a marked initial increase on intravenous NTG but fell progressively and did not differ from that with placebo at 24 hr. Increased exercise tolerance was associated with an increase in maximal heart rate and double product (heart rate X blood pressure), suggesting that direct coronary vasodilation and/or reduced left ventricular volume were the principal determinants of increased exercise tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)
Lifetime risk for patients with mitral valve prolapse of developing severe valve regurgitation requiring surgery.
Authors: Wilcken D E , Hickey A J
Published: June 2011

Severe mitral regurgitation requiring surgery is the most common life-threatening complication of mitral valve prolapse (MVP) and is due to progressive myxomatous change in the valve. We identified all residents of New South Wales, Australia, who had mitral valve surgery for myxomatous valve disease during 1982 and, using these data and the adult population statistics from 1982, estimated the cumulative risk of valve surgery in patients with MVP. In 1982, 50 of the 5.36 million New South Wales residents required surgery for this complication of MVP. Of the 50, 36 were men and 14 were women, which was significantly different from the population sex distribution (p less than 0.02) for mean age +/- SD of 60 +/- 11 years (range, 26-78 years). Using our previously determined 4% prevalence of adult MVP in New South Wales, we estimated the number of male and female patients with MVP at risk for each 5-year age interval and calculated age-specific event rates. The results show that the cumulative risk is minimal below the age of 50 years but then rises steeply, particularly in men. The risks in men aged 50, 60, and 70 years (with 95% confidence intervals) were 1:202 (130-448), 1:53 (37-82), and 1:28 (22-41), respectively. In women, the risk was less than half that in men (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)