bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relation between left ventricular oxygen consumption and pressure-volume area in conscious dogs.
Authors: Nozawa T , Cheng C P , Noda T , Little W C 
Published: June 2012

BACKGROUND
The relation between left ventricular (LV) oxygen consumption (MVO2) and pressure-volume area (PVA) developed in isolated hearts provides a powerful method to understand cardiac energetics. We investigated application of this relation to the intact circulation, determining its response to steady-state and transient load alterations and enhanced contractility in conscious animals.

METHODS AND RESULTS
Eight dogs were instrumented to measure LV pressure (micromanometer), LV volume (three sonomicrometers), and left circumflex and anterior descending coronary artery flows (ultrasonic flowmeter). Data were acquired after recovery from the surgery with the animals awake and unsedated. After administration of hexamethonium and atropine, steady-state loading conditions were changed with phenylephrine or nitroprusside in four to five steps before and during the infusion of dobutamine (6 to 10 micrograms.-1kg.-1min). MVO2 and PVA obtained under steady-state conditions were linearly correlated both before and during dobutamine. The MVO2-PVA relation obtained on a beat-to-beat basis during transient caval occlusion was less linear and not coincident with the steady-state relation. Dobutamine shifted the steady-state MVO2-PVA relation upward in all hearts, increasing the MVO2 axis intercept of the MVO2-PVA relation (P < .01). This intercept correlated with ventricular contractility assessed by the slope (Ees) of the LV end-systolic pressure-volume relation determined by caval occlusion (r = .76, P < .05). The slope of the MVO2-PVA relation increased with dobutamine in seven of eight animals, with the inverse of the slope (representing contractile efficiency) being 31 +/- 6% during control and 24 +/- 6% after dobutamine (P = .06).

CONCLUSIONS
MVO2 and PVA are linearly related during steady-state alterations in loading conditions in conscious dogs but not on a beat-by-beat basis during transient caval occlusion. Increase in contractility by dobutamine produces an upward shift of the MVO2-PVA relation.
Blood pressure and endocrine responses to changes in dietary sodium intake in cardiac transplant recipients. Implications for the control of sodium balance.
Authors: Singer D R , Markandu N D , Buckley M G , Miller M A , Sagnella G A , Lachno D R , Cappuccio F P , Murday A , Yacoub M H , MacGregor G A 
Published: June 2012

BACKGROUND
The role of cardiac extrinsic innervation in the regulation of sodium balance and blood pressure is controversial.

METHODS AND RESULTS
We performed a double-blind study of endocrine and blood pressure responses to 5 days of low- (LS, 10 mmol/d) and 5 days of high- (350 mmol/d) sodium intake in 12 cardiac transplant recipients, 12 matched healthy subjects, and 12 matched subjects with untreated essential hypertension. In transplant recipients on low sodium, supine blood pressure was 137/94 +/- 8/4 (mean +/- SEM) mm Hg and plasma atrial natriuretic peptide (ANP) was 59.3 +/- 6.3 pg/mL; on high sodium, blood pressure was 148/97 +/- 5/3 mmHg (P < .05 for systolic pressure versus LS), and ANP was 94.3 +/- 10.6 pg/mL (P < .01 versus LS), respectively. Plasma ANP for those on each diet was significantly higher in the cardiac transplant recipients than in healthy or hypertensive controls; relative changes in plasma ANP in changing from low- to high-sodium diet were similar in each group. Urinary sodium excretion by the fifth day of each diet was similar in each group. Suppression of plasma renin activity and aldosterone by high-sodium diet was blunted in cardiac transplant recipients compared with healthy subjects (respectively, plasma renin activity: 1.41 +/- 0.30 versus 0.68 +/- 0.21 ng.mL-1 x h-1, P < .05; aldosterone: 391 +/- 35 versus 166 +/- 21 pmol/L, P < .05).

CONCLUSIONS
These results suggest that extensive denervation of the heart does not result in major abnormalities in regulation of large changes in sodium intake and that intact cardiac innervation is not required for plasma ANP responses to altered sodium intake. Blood pressure after cardiac transplantation is sensitive to reduced sodium intake.
Kinetic properties of 99mTc-Q12 in canine myocardium.
Authors: Gerson M C , Millard R W , Roszell N J , McGoron A J , Gabel M , Washburn L C , Biniakiewicz D , Blankenship D , Mallin W H , Elder R C 
Published: June 2012

BACKGROUND
99mTc-Q12 is a new Tc(III) perfusion imaging agent that permits prompt myocardial visualization in humans. We postulated that 99mTc-Q12 myocardial activity is related to actual myocardial blood flow during conditions of myocardial ischemia and pharmacological coronary artery vasodilation and that 99mTc-Q12 shows little or no myocardial redistribution as long as 4 hours after intravenous injection.

METHODS AND RESULTS
In seven anesthetized, open chest dogs, the left circumflex coronary artery was occluded, and dipyridamole (0.32 or 0.56 mg/kg) was infused into the right atrium, followed by 10 mCi of 99mTc-Q12. Myocardial blood flow was measured by radiolabeled microspheres. The animals were euthanized, and a total of 315 myocardial samples were assayed in a well counter for 99mTc activity. One week later, radiolabeled microsphere activity was determined, and myocardial blood flow was calculated. 99mTc activity (y) was related to myocardial blood flow (x) from 0 to 2 mL.g-1 x min-1 by the relation y = 0.64x + 0.35 (r = .88, P = .0001). In 14 additional anesthetized, open chest dogs, an occluder was placed around the left circumflex coronary artery, and an ischemic level of circumflex blood flow was maintained constant over 4 hours as measured by an ultrasonic flowmeter. Dipyridamole (0.56 mg/kg) was infused intravenously beginning 15 minutes after coronary occlusion and then followed by 10 mCi of 99mTc-Q12. Gamma camera images, hemodynamics, microsphere blood flow, and endocardial biopsies (latter in six dogs) were performed at 30, 60, 120, and 240 minutes after 99mTc-Q12 injection. Myocardial blood flow in the distribution of the left anterior descending artery decreased by 29.6% from 30 to 240 minutes (P < .05), whereas left circumflex blood flow increased by 40.4% from 30 to 120 minutes (P < .05) as the dipyridamole hemodynamic effects dissipated. Nevertheless, the ratio of myocardial perfusion defect zone counts to normal myocardial zone counts remained constant over 4 hours, as did the technetium counts from the needle biopsy endocardial samples.

CONCLUSIONS
Over a limited range of myocardial blood flows from 0 to approximately 2 mL.g-1 x min-1, 99mTc-Q12 myocardial activity is related to actual myocardial flow at the time of tracer injection. 99mTc-Q12 shows no evidence of myocardial redistribution.
Noninvasive quantitative evaluation of the morphology of the major pulmonary artery branches in cyanotic congenital heart disease. Angiocardiographic and echocardiographic correlative study.
Authors: Hiraishi S , Misawa H , Hirota H , Agata Y , Horiguchi Y , Fujino N , Yi L H , Yashiro K , Nakae S , Kawada M 
Published: June 2012

BACKGROUND
Precise noninvasive evaluation of pulmonary artery (PA) morphology is extremely important for medical and surgical management of patients with cyanotic heart disease. In this study, the accuracy of two-dimensional echocardiography combined with color Doppler flow mapping to assess the size, stenosis, and atresia of the major PA branches was examined using a new parasternal approach.

METHODS AND RESULTS
With the use of right and left high parasternal windows, we visualized each of the major portions along the right (R-PA) and left (L-PA) pulmonary arteries in 45 of the 47 examinations (96%) in 38 patients with cyanotic heart disease. The patients were between 13 days and 20 years old (mean age, 2.9 years). The internal diameters of the major PA branches were measured at three points along the R-PA (the proximal, mid, and distal portions) and at the proximal and distal portions on the L-PA in systole by both two-dimensional echocardiography and angiography. In addition, the diameter of the stenosis in the PA branch was measured. These PA values as determined by two-dimensional echocardiography correlated well with those obtained by angiography (r = .95 to .97). By two-dimensional echocardiography with color Doppler flow mapping, 17 of 19 lesions with stenoses or atresia of the major PA branches were predicted as defined by angiography (sensitivity, 89.5%; specificity, 100%). Differences between the distal parts of the L-PA and R-PA of > 30% in diameter were determined by angiography in 15 examinations and by two-dimensional echocardiography in 12 examinations (sensitivity, 80%; specificity, 97.4%).

CONCLUSIONS
Our technique permits noninvasive evaluation of the size, stenoses, and atresia of the major portions of the PA branches in patients with cyanotic heart disease both before and after surgery.
Differential expression of the cell adhesion molecules ICAM-1, VCAM-1, and E-selectin in normal and posttransplantation myocardium. Cell adhesion molecule expression in human cardiac allografts.
Authors: Tanio J W , Basu C B , Albelda S M , Eisen H J 
Published: June 2012

BACKGROUND
Cell adhesion molecules (CAMs) have been implicated in cardiac allograft rejection. However, previous studies have used qualitative analysis of immunohistochemical data and did not exclude patients with infection or malignancy.

METHODS AND RESULTS
We analyzed 40 endomyocardial biopsy specimens from 25 cardiac transplant patients and 8 specimens from patients undergoing cardiac surgery. Patients with evidence of infection or malignancy were excluded. Specimens were stained with monoclonal antibodies against ICAM-1, E-selectin, VCAM-1, and PECAM-1 (which labels all vessels). ICAM-1 expression was assessed by counting ICAM-1-positive vessels and dividing by the total number of vessels (measured by PECAM staining). Specimens were scored as positive or negative for VCAM-1 and E-selectin. We also determined whether serum-soluble ICAM-1 levels (sICAM) correlated with rejection by evaluating 145 serum specimens from 48 cardiac transplant patients and 8 specimens from patients undergoing diagnostic cardiac catheterization. ICAM-1 was present on 50% to 60% of vessels in normal and nonrejecting specimens. Specimens with histologically significant rejection (focal moderate, moderate, or severe) had an increased percentage of ICAM-1-positive vessels: focal moderate, 77%; moderate/severe, 92% (P < .01). E-selectin expression did not differ between groups. VCAM-1 frequently was not present on rejecting specimens. No correlation was noted between sICAM levels and the presence or absence of rejection.

CONCLUSIONS
(1) ICAM-1 expression is strongly correlated with histologically significant cardiac allograft rejection. (2) The use of PECAM-1 staining as a vascular marker permits quantitative analysis of ICAM-1 expression. (3) VCAM-1 and E-selectin are not consistently increased during cardiac allograft rejection. (4) sICAM levels do not accurately reflect endomyocardial biopsy results.
Is coronary flow reserve in response to papaverine really normal in syndrome X?
Authors: Chauhan A , Mullins P A , Petch M C , Schofield P M 
Published: June 2012

BACKGROUND
An impaired coronary flow reserve in syndrome X has been demonstrated by many studies. Recently, however, a normal coronary flow reserve in response to papaverine was reported, but the number of patients in these studies was small. The aim of this study was to investigate whether coronary flow reserve in response to intracoronary papaverine is really impaired in syndrome X.

METHODS AND RESULTS
We investigated 53 syndrome X patients (typical angina, a positive exercise test, and completely normal coronary arteries on angiography) and 26 heart transplant patients with normal coronary arteries (control group). All antianginal medications were stopped 48 hours before the study. A 3.6F intracoronary Doppler catheter was positioned in the proximal left anterior descending coronary artery and was connected to a Millar velocimeter. The coronary blood flow velocity at rest and in response to a hyperemic dose of papaverine was measured. Coronary flow reserve was defined as the ratio of hyperemic coronary blood flow velocity in response to papaverine and resting coronary blood flow velocity. The coronary flow reserve (mean +/- SD) in the syndrome X group was 2.72 +/- 1.39. The coronary flow reserve in the control group was significantly higher at 5.22 +/- 1.26 (P < .01). In both groups there was no significant difference in the heart rate or the mean arterial pressure during the study.

CONCLUSIONS
Our study shows that coronary flow reserve in response to intracoronary papaverine is impaired in syndrome X patients.
Intramachine and intermachine variability in transesophageal color Doppler images of pulsatile jets. In vitro studies.
Authors: Fan P H , Anayiotos A , Nanda N C , Yoganathan A P , Cape E G 
Published: June 2012

BACKGROUND
Color Doppler flow mapping is widely used as a marker of severity of valvular regurgitation, and the transesophageal approach has provided high-quality images in patients with poor acoustic windows. However, different instruments produce significantly variable images. Techniques that use jet spatial information to determine the severity of the lesion may need to be derived specifically for the instrument used. Given a lack of standardization of the many commonly used instruments, the goal of this study was to quantify variability between instruments by imaging well-defined jet flow fields created in vitro.

METHODS AND RESULTS
Pulsatile jets were created in vitro using a blood analogue fluid through physiological orifice diameters and imaged from a distal window using six commonly used color Doppler instruments. Transesophageal transducers (5.0 MHz) were used with all instruments studied. Peak jet areas were planimetered and averaged with systematic variations in Nyquist limit, color filter, and sector angle (which produced variations in frame rate). Changes in instrument settings produced significant variation in jet size for all instruments studied. Comparisons within instruments and among instruments were difficult because of preset and ambiguous setting levels. When comparisons were possible between similar settings, variability was dramatic (eg, 57% variability between instruments with very similar Nyquist limits).

CONCLUSIONS
A lack of standardized color Doppler instrument settings prohibits translation of jet area techniques from one instrument to another. This should be taken into consideration when using different machines for clinical study.
Angiogenic-induced enhancement of collateral blood flow to ischemic myocardium by vascular endothelial growth factor in dogs.
Authors: Banai S , Jaklitsch M T , Shou M , Lazarous D F , Scheinowitz M , Biro S , Epstein S E , Unger E F 
Published: June 2012

BACKGROUND
Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen that is angiogenic in vitro and in vivo. It has been hypothesized that VEGF plays a role in myocardial collateral formation; however, the effects of VEGF on collateral flow to ischemic myocardium are unknown.

METHODS AND RESULTS
We studied the effect of VEGF on collateral blood flow in dogs subjected to gradual occlusion of the left circumflex coronary artery (LCx). Beginning 10 days after placement of an LCx-constricting device, VEGF 45 micrograms (n = 9) or saline (n = 12) was administered daily via an indwelling catheter in the distal LCx, at a point just beyond the occlusion. Treatment was maintained for 28 days. Collateral blood flow was determined with microspheres 7 days before treatment, immediately before treatment (day 0), and 7, 14, 21, and 28 days into the treatment period. Collateral blood flow was quantified during chromonar-induced maximal vasodilation and expressed as a collateral zone/normal zone (CZ/NZ) ratio. Treatment with VEGF was associated with a 40% increase in collateral blood flow (final CZ/NZ blood flow ratios of 0.49 +/- 0.06 and 0.35 +/- 0.02 in the VEGF-treated and control groups, respectively, P = .0037) as well as an 89% increase in the numerical density of intramyocardial distribution vessels (> 20 microns diameter) in the CZ (6.6 +/- 1.4 versus 3.5 +/- 0.7 vessels/mm2 in VEGF-treated and control dogs, respectively, P < .05).

CONCLUSIONS
We conclude that intracoronary VEGF enhances the development of small coronary arteries supplying ischemic myocardium, resulting in marked augmentation of maximal collateral blood flow delivery. These results demonstrate the feasibility of pharmacological enhancement of collateral growth and suggest a new therapeutic approach for the treatment of myocardial ischemia.
Origin and significance of double potentials near the atrioventricular node. Correlation of extracellular potentials, intracellular potentials, and histology.
Authors: McGuire M A , de Bakker J M , Vermeulen J T , Opthof T , Becker A E , Janse M J 
Published: June 2012

BACKGROUND
Atrioventricular junctional (AV nodal) reentrant tachycardia can be cured by catheter ablation of the slow pathway, which is part of the reentrant circuit. Previous work has suggested that extracellular double potentials may help identify the site of the slow pathway, but the origin and significance of these potentials are controversial. The aim of this study was to identify the source of these potentials.

METHODS AND RESULTS
Studies were performed in isolated, blood-perfused porcine (n = 8) and canine (n = 4) hearts. Several methods were used to identify the origin of potentials: microelectrode recording, extracellular mapping, pacing from multiple sites, and light microscopy. Two types of double potentials, similar to those found in humans, were found in all hearts. LH potentials consisted of a low-frequency deflection followed by a high-frequency deflection during sinus rhythm or anterior septal pacing. HL potentials consisted of a high-frequency deflection followed by a low-frequency deflection. LH potentials were found close to the coronary sinus orifice. They were caused by asynchronous activation of the sinus septum and the region between the coronary sinus orifice and tricuspid annulus. HL double potentials were found along the tricuspid annulus. They were caused by asynchronous activation of two cell layers. The high-frequency component was caused by depolarization of atrial-type cells in the deep subendocardial layer. The low-frequency component was caused by depolarization of cells with nodal characteristics close to the endocardium. These cells were present around the entire tricuspid annulus, were not part of the compact AV node, and could be dissociated from the bulk of the atria by rapid atrial pacing.

CONCLUSIONS
LH potentials are caused by asynchronous activation of muscle bundles above and below the coronary sinus orifice. Their proximity to the site of the slow pathway is probably serendipity. HL double potentials are caused by asynchronous activation of atrial cells and a band of nodal-type cells close to the tricuspid annulus. The band of nodal-type cells is not part of the compact AV node and may represent the substrate of the slow AV nodal pathway.
Microwave catheter ablation of myocardium in vitro. Assessment of the characteristics of tissue heating and injury.
Authors: Whayne J G , Nath S , Haines D E 
Published: June 2012

BACKGROUND
Radiofrequency (RF) catheter ablation lesion size has been limited by the small volume of tissue directly heated by the RF electrode. Microwave (MW) energy has been proposed as an alternative energy source to generate larger lesions because of its increased volume of direct tissue heating. To further characterize MW ablation of myocardium, we studied the temperature-versus-distance profiles during MW ablation in an in vitro model of perfused and superfused porcine right ventricular free wall.

METHODS AND RESULTS
Radial tissue temperatures in 19 isolated porcine right ventricles were measured and recorded with four fluoroptic thermometry probes placed within the myocardium at 2.5-mm radial increments from the catheter. The MW antenna catheters used were monopolar and helical-coil antennas resonating at 915 and 2450 MHz. Durations of energy delivery for a 915-MHz MW monopolar antenna (60 to 600 seconds) and a 4-mm-tip RF electrode (60 and 300 seconds) were varied to compare time courses of lesion formation. For each lesion, the temperature at the lesion border zone (the isotherm of irreversible tissue injury) was determined. Similar lesion size and temperature profiles were observed for 915- versus 2450-MHz MW antennas and monopolar versus helical-coil MW antennas. Lesion depth for the 915-MHz monopolar antenna increased monoexponentially with a half-time of 170 seconds. The isotherms for all MW antenna designs were not significantly different. The mean isotherm of irreversible tissue injury for MW lesions was not significantly different from the mean isotherm for RF lesions (54.4 degrees C versus 53.6 degrees C, respectively).

CONCLUSIONS
Microwave ablation has the potential to directly heat a greater volume of tissue than RF ablation but only with efficient MW antennas. The primary mechanism of tissue injury for both MW and RF ablation appears to be thermal.
Diurnal variation in blood pressure in patients with biventricular assist devices and retained, nonpumping native hearts.
Authors: Sehested J , Happe E , Ishino K , Hetzer R , Schiessler U , Schifter S 
Published: June 2012

BACKGROUND
Studies indicate that centrally mediated rhythms in sympathetic tone play a prominent role in diurnal cardiovascular variability. Recent evidence from heart transplant recipients, in whom blood pressure does not decline during sleep despite normal variability in plasma norepinephrine, however, suggests that afferent cardiac nervous traffic is necessary for the generation of diurnal variability. This implies that in the presence of an innervated heart excluded from the systemic circulation, blood pressure would still decrease during sleep. To assess this hypothesis, we studied 24-hour blood pressure, heart rate, and neuroendocrine variability in patients with biventricular assist devices in whom the retained native hearts had ceased to pump.

METHODS AND RESULTS
Eight patients were free of medication and were studied every 3 hours. Pump rates and output were kept constant throughout the study. Blood pressure showed a significant decline during sleep, as did norepinephrine and epinephrine (all P < .05). Atrial natriuretic factor showed a significant increase around midnight (P < .01). Significantly elevated levels were found for all hormones studied except for aldosterone and endothelin.

CONCLUSIONS
Our results suggest that diurnal variations in cardiac function or in catecholamine levels (indicative of sympathetic activity) as found in cardiac transplant recipients alone are not responsible or sufficient for producing a nocturnal drop in blood pressure. The presence of an innervated heart appears crucial in this respect. This could be of importance for the understanding of circadian cardiovascular pathophysiology.