bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital angiographic measurement of radiographic contrast material kinetics for estimation of myocardial perfusion.
Authors: Whiting J S , Drury J K , Pfaff J M , Chang B L , Eigler N L , Meerbaum S , Corday E , Nivatpumin T , Forrester J S , Swan H J
Published: June 2011

We studied the use of digital angiography for the quantification of regional myocardial perfusion in the dog using selective left coronary arterial injection of radiographic contrast material as a flow dilution indicator. We developed algorithms for generating time-intensity curves from regions of interest over the proximal coronary artery and the myocardium and for densitometric error correction by subtraction of the intensity curve over a small lead blocker before logarithmic transformation. The resultant myocardial time-density curves were analyzed for time from injection to peak concentration (TPC) and for exponential washout rate (k). A linear correlation was found between absolute coronary arterial blood flow and both k (slope = 0.13, r = .85) and 1/TPC (slope = 0.18, r = .85). Reproducibility of TPC and k for repeated studies was 11% and 16%. Induced hyperemia significantly improved the sensitivity to stenosis by increasing the average difference in TPC and k between regions served by normal and stenotic coronary arteries to 65% and 80%, respectively. By combining selective coronary arterial injection with the left lateral x-ray projection it was possible to avoid most overlap of regional perfusion beds in the dog. This study suggests that contrast dilution measurements made during digital coronary angiography provide a means for assessing the hemodynamic significance of stenoses and the efficacy of therapeutic interventions.
The cellular electrophysiologic changes induced by high-energy electrical ablation in canine myocardium.
Authors: Levine J H , Spear J F , Weisman H F , Kadish A H , Prood C , Siu C O , Moore E N
Published: June 2011

High-energy electrical ablation is a new experimental approach to control arrhythmias. In this study, the cellular electrophysiologic effects of high-energy shocks (5 to 40 J) delivered in vitro to 14 epicardial tissues from 11 dogs were studied in an attempt to understand the nature and extent of injury as well as potential arrhythmogenic mechanisms. In addition, this preparation was used to test the importance of cathode-anode configuration, current density, and fiber orientation in the induction of tissue injury in vitro. Electrophysiologic abnormalities were noted up to 10 mm from the electrode wall, and their extent was determined in part by current density and the cathode-anode orientation. A decrease in resting membrane potential, action potential amplitude, and dV/dT occurred in all tissues after high-energy shocks, which was worst nearest the cathode and of graded severity at increasing distances from the cathode. The most severe effects were noted with high current densities and in tissues located between the cathode and anode. In addition, impaired impulse conduction and abnormal repolarization were documented. Histologic study demonstrated contraction band necrosis immediately after delivery of high-energy shocks. The extent and distribution of the contraction bands was in part dependent on the energy delivered and the cathode-anode configuration. These findings suggest potential mechanisms for arrhythmogenesis and altered regional hemodynamic abnormalities that occur in vivo.
Disparate effects of the calcium-channel blockers, nifedipine and verapamil, on alpha 2-adrenergic receptors and thromboxane A2-induced aggregation of human platelets.
Authors: Johnson G J , Leis L A , Francis G S
Published: June 2011

Calcium-channel blockers inhibit human platelet aggregation in vitro and ex vivo. To further evaluate the mechanism(s) responsible for the inhibition induced by this structurally heterogeneous group of compounds, we studied the effect of nifedipine and verapamil on human platelet aggregation in vitro. Neither 10 microM nifedipine nor 10 microM verapamil consistently inhibited the aggregation response of platelet-rich plasma to threshold concentrations of ADP, sodium arachidonate, epinephrine, or collagen. However, both 10 microM nifedipine and 10 microM verapamil epinephrine-potentiated, thromboxane A2 (TXA2)-induced aggregation of aspirin-incubated, gel-filtered platelets. Aggregation of similarly prepared platelets induced by TXA2 alone was abolished by 10 microM nifedipine but not by 10 microM verapamil. Even 100 microM verapamil gave only partial and inconsistent inhibition of aggregation. Both drugs had essentially the same effects on platelet aggregation induced by the stable endoperoxide and TXA2 mimic, U46619, with or without epinephrine. Neither 10 microM nifedipine nor 10 microM verapamil elevated platelet cyclic AMP. Verapamil (10 microM) inhibited binding of [3H]-yohimbine (an alpha 2-adrenergic receptor antagonist) to intact human platelets (KD 10.5 nM vs 2.4 nM for control platelets) without altering the number of binding sites. In contrast, 10 microM nifedipine had no effect on KD or number of binding sites. These results indicate that nifedipine and verapamil inhibit epinephrine-potentiated, TXA2-induced human platelet aggregation by different mechanisms. Verapamil inhibits the epinephrine contribution to the aggregation response by blocking alpha 2-adrenergic receptor binding. Nifedipine blocks the platelet response to TXA2 without affecting alpha-adrenergic receptor binding. These observations have potential clinical implications with regard to the mechanisms by which calcium-channel blockers inhibit vascular spasm and myocardial ischemia.
Myocardial relaxation: effects of preload on the time course of isovolumetric relaxation.
Authors: Gaasch W H , Carroll J D , Blaustein A S , Bing O H
Published: June 2011

We studied the effect of an isolated increase in preload on isovolumetric relaxation in the intact dog heart and isometric relaxation in isolated cardiac muscle (dog and rat) preparations. In eight anesthetized dogs, 8 to 12 ml of blood was infused into the left ventricle during a single diastole. The exponential time constant (T) of isovolumetric relaxation was measured in single-beat experiments in which the left ventricular systolic pressure increased (112 +/- 2 to 128 +/- 3 mm Hg; p less than .05, n = 62). In a second series of experiments, left ventricular systolic pressure was held constant (109 +/- 2 to 107 +/- 2 mm Hg; p = NS, n = 23) by simultaneous ventricular infusion and aortic unloading. In the first protocol, T increased from 28.0 +/- 0.4 to 30.7 +/- 0.4 msec (p less than .05), whereas in the second protocol (constant systolic pressure) there was no change in T. The time course of isometric relaxation was also studied in six rat left ventricular papillary muscles and four dog right ventricular trabecular muscles. Preload was varied from 30% to 100% of the peak of the isometric length-tension curve in each muscle. Over this wide range of preload, the isometric force decline recordings were superimposable as long as the comparisons were made at equal levels of total load. Thus an isolated increase in preload does not influence the time course of isovolumetric relaxation.
Left ventricular performance and contractility before and after volume infusion: a comparative study of preterm and full-term newborn lambs.
Authors: Baylen B G , Ogata H , Ikegami M , Jacobs H , Jobe A , Emmanouilides G C
Published: June 2011

We studied left ventricular performance and contractility after volume loading in lambs at 122 days (group I, n = 9) and 139 days gestational age (group II, n = 9) and in 8-day-old full-term lambs (group III, n = 7). All were mechanically ventilated; each preterm lamb was treated with surfactant to stabilize pulmonary function and the ductus arteriosus was occluded with an inflated catheter balloon. Cineangiograms, left ventricular and vascular pressures, and the isovolumetric index of contractility, first derivative of left ventricular pressure (dP/dt), were recorded before and after three successive whole blood volume infusions of 10 ml/kg (total 30 ml/kg). The left ventricular end-diastolic volume per kilogram and stroke volume per kilogram increased significantly in all groups after volume infusion; these measurements and heart rate and systemic vascular resistance did not differ significantly between the groups either before or after the infusions. The left ventricular peak dP/dt did not change significantly within the groups during the volume infusions. The left ventricular stroke work was greatest in full-term animals and increased significantly in all groups after volume infusion. Thus, the left ventricles of the preterm and full-term lambs had quantitatively similar Frank-Starling responses and there was no increase in contractility during the infusions of whole blood. However, the left ventricle of the full-term lamb is capable of generating greater stroke work than that of the preterm lamb. These findings may contribute to the understanding of development aspects of postnatal circulatory adaptation.
Therapy with cyclosporine in experimental murine myocarditis with encephalomyocarditis virus.
Authors: Monrad E S , Matsumori A , Murphy J C , Fox J G , Crumpacker C S , Abelmann W H
Published: June 2011

To explain the progression from infectious viral myocarditis to congestive cardiomyopathy an infection/immune hypothesis has been proposed stating that the primary viral process incites an excessive or disordered immunologic response against the myocardium. To test whether one form of immunosuppressive therapy might ameliorate this process, we used cyclosporine in a murine preparation of infectious myocarditis (encephalomyocarditis [EMC] virus), which has been shown to result in a congestive cardiomyopathy pathologically similar to that seen in man. Eight-week-old male DBA-2 mice were infected with EMC virus and randomized to a treatment or control group. Cyclosporine (25 mg/kg/day) was administered subcutaneously for 3 weeks, starting (1) at 1 week after infection during viral replication, and (2) at 3 weeks after infection, after the period of active viral replication. In mice treated during viral replication there was a significantly higher mortality rate compared with that of control mice (15/21 vs 9/29, p = .01). There was no evident reduction in myocardial pathology (inflammation, necrosis, or calcification) in the treated compared with the control groups. In mice treated after the period of viral replication, there was no improvement in mortality (8/22 vs 2/19, NS) compared with control. Treated mice showed no reduction in myocardial histopathologic lesions. Furthermore, treated mice had significantly greater heart weight/body weight ratios (1.3 +/- 0.4% vs 1.0 +/- 0.3%, p less than .005), lung weight/body weight ratios (1.1 +/- 0.5% vs 0.8 +/- 0.3%, p less than .05), and liver weight/body weight ratios (6.0 +/- 0.8% vs 5.4 +/- 0.6%, p less than .005) than control mice, suggesting more severe myocardial failure.(ABSTRACT TRUNCATED AT 250 WORDS)
The relationship between plasma levels of immunoreactive atrial natriuretic hormone and hemodynamic function in man.
Authors: Bates E R , Shenker Y , Grekin R J
Published: June 2011

To evaluate the relationship between plasma levels of immunoreactive atrial natriuretic hormone (IR-ANH) and different hemodynamic parameters in man, we studied 34 patients undergoing right heart catheterization. Plasma levels of IR-ANH in blood samples withdrawn from the femoral vein (n = 28), right ventricle (n = 27), and left ventricle (n = 17) were determined by radioimmunoassay. Right atrial pressure, pulmonary arterial wedge pressure, heart rate, and mean arterial pressure were found to be independent and significant predictors of IR-ANH plasma levels. The closest correlations were between right atrial pressure and either right ventricular IR-ANH levels (r = .78, p greater than .001) or femoral vein IR-ANH levels (r = .52, p less than .006). Five patients with isolated left ventricular failure had elevated IR-ANH levels out of proportion to their right atrial pressure levels. Pulmonary arterial wedge pressure also correlated with right ventricular IR-ANH levels (r = .46, p less than .002) and with femoral vein IR-ANH levels (r = .58, p less than .002). A single patient with isolated right heart failure had markedly elevated IR-ANH levels despite normal pulmonary arterial wedge pressure. Right ventricular levels were twice femoral vein levels and were closely correlated (181 +/- 40 vs 90 +/- 20 pmol/liter; r = .90, p less than .001). Right ventricular and left ventricular levels were almost identical (155 +/- 46 vs 146 +/- 43 pmol/liter; r = .99, p less than .001). Patients with volume overload states had elevated IR-ANH levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Rate control of physiologic pacemakers by central venous blood temperature.
Authors: Alt E , Hirgstetter C , Heinz M , Blömer H
Published: June 2011

Heart rate and central venous blood temperature (CVT) were measured in 31 people with different exercise capacities by means of a thermistor integrated into a lead that was placed in the right ventricle. Bicycle ergometric and treadmill stress tests with increasing workloads were performed. The maximum increase in CVT with ergometric exercise was found to be 1.3 degrees C at 250 W in healthy young volunteers and 1.0 degrees C at 125 W in cardiac patients. Despite a relatively greater increase in CVT in the elderly patients compared with the volunteers, the correlation between the increase in CVT and that in heart rate at the end of each exercise stage was found to be very high (r = .9693 in volunteers and r = .9864 in cardiac patients), independent of physical fitness. Even with everyday activities such as walking there was a marked increase in CVT. Due to its close relationship to human metabolism, CVT represents a good parameter for physiologic control of pacing rate.
A prospective evaluation of the Björk-Shiley, Hancock, and Carpentier-Edwards heart valve prostheses.
Authors: Bloomfield P , Kitchin A H , Wheatley D J , Walbaum P R , Lutz W , Miller H C
Published: June 2011

From 1975 to 1979, 540 patients undergoing valve replacement were entered into a randomized trial and received either a Björk-Shiley (273 patients) or a porcine heterograft prosthesis (initially a Hancock valve [107 patients] and later a Carpentier-Edwards prosthesis [160 patients]). Two hundred and sixty-two patients required mitral valve replacement, 210 required aortic valve replacement, 60 required mitral and aortic valve replacement, and eight also required associated tricuspid valve replacement (six mitral valve replacement; two mitral plus aortic valve replacement). Analysis of 34 preoperative and operative variables showed the treatment groups to be well randomized. In-hospital mortality was not significantly different among patients receiving the three prostheses for aortic valve replacement (7.6% overall) and mitral plus aortic valve replacement (10% overall), but there was a higher in-hospital mortality for patients undergoing mitral valve replacement with the Carpentier-Edwards prosthesis (15.5% compared with 8.8% overall; p = .03). This difference could not be explained on the basis of any preoperative or operative variable. Median follow-up was 5.6 (range 2.8 to 8.3) years. Actuarial survival after mitral valve replacement was 56.7 +/- 7.0% at 7 years, that after aortic valve replacement was 69.6 +/- 9.6% at 7 years, and that after mitral plus aortic valve replacement was 62.5 +/- 20.0% at 7 years. There was no significant difference in actuarial survival of patients receiving the three prostheses within the mitral, aortic, and mitral plus aortic valve replacement groups, nor was there a difference when these groups were amalgamated. Thirty-seven patients required reoperation for valve failure (15 with Björk-Shiley, 12 with Hancock, and 10 with Carpentier-Edwards valves; p = NS) and 11 died at reoperation (four with Björk-Shiley, four with Hancock, and three with Carpentier-Edwards valves; overall operative mortality 29.7%). Up to 7 years after surgery, there was no significant difference in the incidence of thromboembolism in patients with different prostheses undergoing mitral or aortic valve replacement. There were too few patients undergoing mitral plus aortic valve replacement for meaningful comparison. There was no significant beneficial effect of anticoagulants in patients undergoing mitral or aortic valve replacement with porcine prostheses, but patients were not randomly allocated to anticoagulant treatment. All patients with Björk-Shiley prostheses received anticoagulants.(ABSTRACT TRUNCATED AT 400 WORDS)
The effect of nitroglycerin on forearm arterial distensibility.
Authors: Smulyan H , Mookherjee S , Warner R A
Published: June 2011

Nitroglycerin acts, in part, to reduce arterial impedance, and thus left ventricular work. The reduction in arterial impedance is largely attributable to a fall in systemic vascular resistance, but may also be due to an increased distensibility of the arterial tree. In this study, volume distensibility of forearm arteries was calculated from measurements of pulse-wave velocity before and during intravenous nitroglycerin infusion. Since a fall in blood pressure itself increases arterial distensibility, the induced blood pressure change was controlled as a variable by repeating the measurements with the subject's forearm in a plastic cylinder and repeating the measurements at a variety of altered cylinder pressures. At every studied pressure, nitroglycerin infusion increased forearm arterial distensibility, demonstrating another way in which nitroglycerin reduces left ventricular afterload. Since the pulsatile portion of cardiac work is approximately 10% of total work, the magnitude of this nitroglycerin effect on cardiac function is probably small.
Abrupt withdrawal of beta-blockade therapy in patients with myocardial infarction: effects on infarct size, left ventricular function, and hospital course.
Authors: Croft C H , Rude R E , Gustafson N , Stone P H , Poole W K , Roberts R , Strauss H W , Raabe D S , Thomas L J , Jaffe A S
Published: June 2011

The effects of abrupt withdrawal or continuation of beta-blockade therapy during acute myocardial infarction were evaluated in 326 patients participating in the Multicenter Investigation of the Limitation of Infarct Size (MILIS). Thirty-nine patients previously receiving a beta-blocker and randomly selected for withdrawal of beta-blockers and placebo treatment during infarction (group 1) were compared with 272 patients previously untreated with beta-blockers who were also randomly assigned to placebo therapy (group 2). There were no significant differences between the two groups in MB creatine kinase isoenzyme (15.8 +/- 10.9 vs 18.2 +/- 14.4 g-eq/m2, respectively) estimates of infarct size, radionuclide-determined left ventricular ejection fractions within 18 hr of infarction (0.44 +/- 0.15 vs 0.47 +/- 0.16) or 10 days later (0.42 +/- 0.14 vs 0.47 +/- 0.16), creatine kinase-determined incidence of infarct extension (13% vs 6%), congestive heart failure (43% vs 37%), nonfatal ventricular fibrillation (5% vs 7%), or in-hospital mortality (13% vs 9%). Patients in group 1 had more recurrent ischemic chest pain (p = .002) within the first 24 hr after infarction, but not thereafter. However, this did not appear to be related to a rebound increase in systolic blood pressure, heart rate, or double product. In a separate analysis, 20 propranolol-eligible group 1 patients randomly selected for withdrawal of beta-blockade (group 3) were compared with 15 patients randomly selected for continuation of prior beta-blockade therapy (group 4). This comparison yielded similar results. These data indicate that the beta-blockade withdrawal phenomenon is not a major clinical problem in patients with acute myocardial infarction. beta-Blockade therapy can be discontinued abruptly during acute myocardial infarction if clinically indicated.
Balloon dilatation of calcific aortic stenosis in elderly patients: postmortem, intraoperative, and percutaneous valvuloplasty studies.
Authors: McKay R G , Safian R D , Lock J E , Mandell V S , Thurer R L , Schnitt S J , Grossman W
Published: June 2011

To assess the safety and efficacy of percutaneous balloon valvuloplasty in calcific aortic stenosis, balloon dilatation of critically stenosed, calcified aortic valves was performed in five postmortem hearts, in five patients intraoperatively before aortic valve replacement, and in two elderly patients percutaneously at the time of diagnostic catheterization. The etiology of aortic stenosis in the 12 cases was rheumatic in two, congenital bicuspid calcific stenosis in one, and senile calcific degenerative stenosis in the remaining nine. Prevalvuloplasty examination in the 10 postmortem and intraoperative cases revealed rigid valve leaflets with commissural fusion in three valves and extensive nodular calcification in seven. Subsequent balloon dilatation with 15 to 18 mm valvuloplasty balloons resulted in decreased cusp rigidity and increased mobility of valve leaflets in all cases, without evidence of tearing of valve leaflets, disruption of the valvular ring, or liberation of calcific or valvular debris. In the three valve specimens with commissural fusion, balloon dilatation resulted in partial or complete separation of leaflets along fused commissures. In two cases with extensive nodular calcification, balloon dilatation resulted in a fracture of a calcified leaflet that was evident on both gross and radiologic examination. After postmortem and intraoperative studies, percutaneous catheter valvuloplasty was performed at the time of diagnostic catheterization in two elderly patients (93- and 85-year-old women) with long-standing calcific aortic stenosis. Balloon dilatation with 12 to 18 mm balloons resulted in significant decreases in aortic gradients and significant increases in cardiac index and aortic valve area in both patients. Percutaneous valvuloplasty in both patients resulted in a mild increase in aortic insufficiency and no evidence of embolic phenomena.
The influence of preload and heart rate on Doppler echocardiographic indexes of left ventricular performance: comparison with invasive indexes in an experimental preparation.
Authors: Wallmeyer K , Wann L S , Sagar K B , Kalbfleisch J , Klopfenstein H S
Published: June 2011

We evaluated the ability of Doppler echocardiography to assess left ventricular performance in six open-chest dogs studied under various conditions. Intravenous infusions of nitroglycerin were used to vary preload, atrial pacing was used to control heart rate, and changes in inotropic state were induced by two different doses of dobutamine (5 and 10 micrograms/kg/min iv) and by administration of propranolol (1 mg/kg iv). Left ventricular anterior wall myocardial segment length was used as an index of preload. Maximum aortic blood flow, peak acceleration of aortic blood flow, and dP/dt were measured with an electromagnetic flow probe around the ascending aorta and a high-fidelity pressure transducer in the left ventricle. A continuous-wave Doppler transducer applied to the aortic arch was used to measure peak aortic blood velocity, mean acceleration, time to peak velocity, and the systolic velocity integral. The differences between mean values obtained under different inotropic conditions were significant at the p less than .01 level for peak velocity and at the p less than .05 level for mean acceleration. Within a given animal, Doppler measurements of peak velocity correlated very closely with maximum aortic flow (r = .96), maximum acceleration of aortic flow (r = .95), and with maximum dP/dt (r = .92). Mean acceleration measured by Doppler echocardiography also correlated very closely with conventional indexes, but was subject to greater interobserver variability. Doppler measurements of time to peak and the systolic velocity integral correlated less well with conventional hemodynamic indexes.(ABSTRACT TRUNCATED AT 250 WORDS)
Paradoxical and pseudoparadoxical interventricular septal motion in patients with right ventricular volume overload.
Authors: Feneley M , Gavaghan T
Published: June 2011

Cross-sectional echocardiographic measurements of normalized septal curvature (NSC), systolic anterior motion of the center of the left ventricular cavity (CAM), and the M mode ratio of left ventricular posterior wall epicardial motion (PEM) to posterior wall thickening (PWT) were made in eight normal subjects, 16 patients with right ventricular volume overload (RVVO) and five with pressure overload (RVPO). Paradoxical M mode septal motion was confined to early systole in six patients with RVVO (group I) and was sustained in 10 (group II). Similar end-diastolic septal flattening was observed in RVVO group I (NSC 0.50 +/- 0.16 [SD]) and group II (0.49 +/- 0.23) when compared with the normal group (0.83 +/- 0.07, both p less than .005). NSC increased in both RVVO groups during the first one-third of systole (p less than .002) to values not significantly different from normal, but did not change significantly thereafter. CAM in RVVO group II (5.4 +/- 2.2 mm) exceeded CAM in both the normal group (1.8 +/- 1.9 mm, p less than .001) and group I (2.1 +/- 1.4 mm, p less than .005). Similarly, the PEM/PWT ratios in group II (mean 2.94; range 2.13 to 8.0) exceeded those in both the normal group (mean 1.59; range 1.11 to 2.13, p less than .01) and group I (mean 1.32; range 1.10 to 1.67, p less than .01). In the RVPO group, CAM was significant, the PEM/PWT ratios were lower than normal (p less than .01), and marked end-diastolic septal flattening was incompletely corrected during early systole, after which the septum was flattened further until end-systole (p less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)
Advantages and applications of the centerline method for characterizing regional ventricular function.
Authors: Sheehan F H , Bolson E L , Dodge H T , Mathey D G , Schofer J , Woo H W
Published: June 2011

We sought to identify theoretical advantages and applications of the centerline method for quantitative assessment of regional ventricular function. Motion was measured along 100 chords constructed perpendicular to a centerline drawn midway between the end-diastolic and end-systolic contours, and normalized for heart size. Abnormality was expressed in units of standard deviations from the mean motion in a normal reference population to indicate both the severity and significance of the wall motion abnormality. The mean abnormality averaged over 100 chords correlated highly with the area ejection fraction (r = .97). The centerline method uses a "sliding window" to measure motion where it is abnormal, because assessment of wall motion in predefined regions of the ventricular contour underestimates abnormality. From the 100 data points, the extent (% of contour) of regional abnormalities can also be determined. The severity of hypokinesis at the site of acute myocardial infarction correlated better with infarct size estimated from creatine kinase release (r = -.78) than did the ejection fraction or the circumferential extent of hypokinesis. Because the centerline method measures motion along locally determined vectors, and requires no apex, origin, coordinate system, or geometric reference figure, it can be applied to contours as dissimilar as the 60 degree left anterior oblique projection of the left ventricle and the 75 degree left anterior oblique projection of the right ventricle.
Quantitation of mitral regurgitation by Doppler echocardiography.
Authors: Blumlein S , Bouchard A , Schiller N B , Dae M , Byrd B F , Ports T , Botvinick E H
Published: June 2011

The evaluation and care of patients with mitral regurgitation would be facilitated by an easy, reproducible and noninvasive method that could quantitate the hemodynamic burden. In this study, we describe a new Doppler echocardiographic method that measures the regurgitant fraction and we compare it with angiographic and scintigraphic methods. A total of 27 patients with mitral regurgitation were evaluated by echocardiography and either cardiac catheterization or scintigraphy. With two-dimensional echocardiography, diastolic and systolic volumes were measured to derive the left ventricular stroke volume (LVSV). The forward stroke volume (FSV) was obtained from the product of M mode-derived aortic valve area and ascending aortic flow velocity integral assessed by continuous-wave Doppler. Regurgitant fraction was calculated as follows: (LVSV - FSV)/LVSV. Comparisons showed that regurgitant fraction calculated by Doppler echocardiography correlated with regurgitant fraction determined by both cardiac catheterization (r = .82) and by scintigraphy (r = .89). There was, however, an important interobserver variability within each method: 10%, 13%, and 11% for Doppler echocardiography, angiography, and scintigraphy, respectively. In conclusion, Doppler echocardiography can be used to quantitate mitral regurgitation. Serial noninvasive determinations of regurgitant fraction may be useful in the evaluation of therapy and in the follow-up of patients with mitral insufficiency.
Improvement of left ventricular contractile function by exercise training in patients with coronary artery disease.
Authors: Ehsani A A , Biello D R , Schultz J , Sobel B E , Holloszy J O
Published: June 2011

To determine whether prolonged, intense exercise training can improve left ventricular function in patients with coronary artery disease, we studied 25 patients, 52 +/- 2 years old (mean +/- SE), who completed a 12 month program of endurance exercise training and 14 additional patients with comparable maximal exercise capacities and ejection fractions who did not exercise. The training program consisted of endurance exercise of progressively increasing intensity, frequency, and duration. During the last 3 months the patients were running an average of 18 miles/week, or doing an equivalent amount of exercise on a cycle ergometer. Maximal attainable VO2 increased 37% (p less than .001). Of the 10 patients with effort angina, five became asymptomatic, three experienced less angina, and two were unchanged after training. Ejection fraction was determined by equilibrium radionuclide ventriculography. At rest, ejection fraction was 53 +/- 3% before and 54 +/- 3% after training (p = NS). Ejection fraction did not change during maximal supine exercise before training (52 +/- 3%), but after training it increased to 58 +/- 3% (p less than .01). During maximal exercise, systolic blood pressure and the rate-pressure product were higher after training. The systolic blood pressure-end-systolic volume relationship was shifted upward and to the left, with an increase in maximal systolic blood pressure (p less than .001) and a smaller end-systolic volume (p less than .05), providing evidence for an improvement in contractile state after training. In patients who did not participate in training neither this relationship nor the ejection fraction response to exercise was changed after 12 months.(ABSTRACT TRUNCATED AT 250 WORDS)
Additive effects of dobutamine and amrinone on myocardial contractility and ventricular performance in patients with severe heart failure.
Authors: Gage J , Rutman H , Lucido D , LeJemtel T H
Published: June 2011

The effects of amrinone, dobutamine, and a combination of the two drugs on peak positive left ventricular dP/dt and left ventricular performance were evaluated in 11 patients with chronic congestive heart failure. When administered alone, both dobutamine (10.9 micrograms/kg/min) and intravenous amrinone (1.9 mg/kg/min) significantly increased left ventricular dP/dt and performance. When compared with dobutamine alone, the addition of amrinone resulted in further increases in left ventricular dP/dt and cardiac index (to 1319 +/- 419 from 1202 +/- 376 mm Hg/sec, p less than .002, and to 3.56 +/- 0.78 from 3.04 +/- 0.67 liters/min/m2, p less than .01, respectively). The combination also induced a further reduction in left ventricular end-diastolic pressure (to 15.3 +/- 11.3 from 18.2 +/- 10.3 mm Hg, p less than .05) when compared with amrinone alone. The combination of dobutamine and amrinone increased heart rate slightly when compared with either drug alone, but did not further reduce systemic arterial pressure when compared with amrinone alone. The dose-response curve of left ventricular dP/dt and performance during titration of dobutamine with and without the addition of intravenous amrinone was evaluated in seven patients. The addition of amrinone to any dose of dobutamine produced higher cardiac index and lower systemic vascular resistance than dobutamine or amrinone alone. Thus, when compared with dobutamine alone in patients with chronic congestive heart failure, the addition of intravenous amrinone to dobutamine results in an additive improvement in left ventricular performance throughout the dose range.
Continuous-wave Doppler echocardiographic detection of pulmonary regurgitation and its application to noninvasive estimation of pulmonary artery pressure.
Authors: Masuyama T , Kodama K , Kitabatake A , Sato H , Nanto S , Inoue M
Published: June 2011

Continuous-wave Doppler echocardiography was used to estimate pulmonary artery pressures by measuring pulmonary regurgitant flow velocity in 21 patients with pulmonary hypertension (mean pulmonary artery pressure greater than or equal to 20 mm Hg) and 24 patients without pulmonary hypertension. The pulmonary regurgitant flow velocity patterns, characterized by a rapid rise in flow velocity immediately after closure of the pulmonary valve and a gradual deceleration until the next pulmonary valve opening, were successfully obtained in 18 of the 21 patients with pulmonary hypertension and in 13 of the 24 patients without pulmonary hypertension. As pulmonary artery pressure increased, pulmonary regurgitant flow velocity became higher; the pulmonary artery-to-right ventricular pressure gradient in diastole (PG) was estimated from the pulmonary regurgitant flow velocity (V) by means of the simplified Bernoulli equation (PG = 4V2). The Doppler-determined pressure gradient at end-diastole correlated well with the catheter measurement of the pressure gradient at end-diastole (r = .94, SEE = 3 mm Hg) and with pulmonary artery end-diastolic pressure (r = .92, SEE = 4 mm Hg). The peak of Doppler-determined pressure gradient during diastole correlated well with mean pulmonary artery pressure (r = .92, SEE = 5 mm Hg). Thus continuous-wave Doppler echocardiography was useful for noninvasive estimation of pulmonary artery pressures.
Ten year survival after coronary artery bypass surgery for angina in patients aged 65 years and older.
Authors: Rahimtoola S H , Grunkemeier G L , Starr A
Published: June 2011

We have assessed the long-term results of coronary bypass surgery for angina from 1974 to 1983 in 1304 patients aged 65 years and older (group 1). Using actuarial techniques, we determined that the 5 year and 10 year survival rates for patients 65 years old or older were 81 +/- 2% and 65 +/- 3% (mean +/- SE), respectively. The patients aged 65 years and older were further subdivided into those aged 65 to 74 years (group 1a) and 75 to 84 years (group 1b) and were compared with 1700 patients aged 55 to 64 years (group 2). The operative mortality in the three subgroups was 3%, 3%, and 2%, respectively (p = NS). For coronary bypass surgery, the duration of hospital stay was significantly longer (p less than .0001) by a mean of 1 to 2 days for group 1 patients and the cost of hospitalization was higher by a mean of $ 700 (p = .25). The cost of hospitalization was significantly higher only for group 1b patients (p = .005). The 5 year survival rates for the three subgroups (1a, 1b, and 2) were 83 +/- 2%, 73 +/- 5%, and 91 +/- 1%, respectively, and the 10 year survival rates were 66 +/- 3%, 65 +/- 7% (7 year rate for subgroup 1b), and 77 +/- 2%, respectively. The lower survival rates for subgroups 1a and 1b were significant (p less than .001); however, this lower survival was only seen in men.(ABSTRACT TRUNCATED AT 250 WORDS)
Ventricular coupling in constrictive pericarditis.
Authors: Santamore W P , Bartlett R , Van Buren S J , Dowd M K , Kutcher M A
Published: June 2011

Because of the close anatomic association, the volume or pressure in one ventricle can directly influence the volume and pressure in the other ventricle. Disease states that reduce pericardial compliance should accentuate this coupling between the ventricles. We examined this hypothesis in six dogs. Constrictive pericarditis was induced by injecting an irritant mixture into the pericardial cavity. Three to 4 weeks after this injection, the hearts were removed and placed in cool cardioplegic solution. Balloons were inserted into each ventricle and the pressure and volume changes caused by increasing the contralateral ventricular volume were measured. Compared with that in a control group of four dogs, the coupling between the ventricles was significantly augmented in the group with constrictive pericarditis. All the measured changes in ventricular pressure or volume caused by increasing contralateral ventricular pressure or volume were significantly greater (p less than .05) in the group with constrictive pericarditis. The results of these experiments show increased coupling between the ventricles with constrictive pericarditis, which helps to explain some of the signs and symptoms of constrictive pericarditis.
The potential gradient field created by epicardial defibrillation electrodes in dogs.
Authors: Chen P S , Wolf P D , Claydon F J , Dixon E G , Vidaillet H J , Danieley N D , Pilkington T C , Ideker R E
Published: June 2011

Knowledge of the potential gradient field created by defibrillation electrodes is important for the understanding and improvement of defibrillation. To obtain this knowledge by direct measurements, potentials were recorded from 60 epicardial, eight septal, and 36 right ventricular transmural electrodes in six open-chest dogs while 1 to 2 V shocks were given through defibrillation electrodes on the right atrium and left ventricular apex (RA. V) and on the right and left ventricles (RV .LV). The potential gradient field across the ventricles was calculated for these low voltages. Ventricular fibrillation was electrically induced, and ventricular activation patterns were recorded after delivering high-voltage shocks just below the defibrillation threshold. With the low-voltage shocks, the potential gradient field was very uneven, with the highest gradient near the epicardial defibrillation electrodes and the weakest gradient distant from the defibrillation electrodes for both RA. V and RV .LV combinations. The mean ratio of the highest to the lowest measured gradient over the entire ventricular epicardium was 19.4 +/- 8.1 SD for the RA. V combination and 14.4 +/- 3.4 for the RV .LV combination. For both defibrillation electrode combinations, the earliest sites of activation after unsuccessful shocks just below the defibrillation threshold were located in areas where the potential gradient was weak for the low-voltage shocks. We conclude that there is a markedly uneven distribution of potential gradients for epicardial defibrillation electrodes with most of the voltage drop occurring near the electrodes, the potential gradient field is significant because it determines where shocks fail to halt fibrillation, and determination of the potential gradient field should lead to the development of improved electrode locations for defibrillation.
The effect of chemical ablation of the endocardium on ventricular fibrillation threshold.
Authors: Damiano R J , Smith P K , Tripp H F , Asano T , Small K W , Lowe J E , Ideker R E , Cox J L
Published: June 2011

The purpose of this study was to examine the effects of ablation of the superficial endocardium and Purkinje network on left ventricular fibrillation threshold. Lugol's solution was applied through small ventriculotomies to the left and right ventricular endocardium of 10 dogs on cardiopulmonary bypass. Two control groups of five animals each underwent either endocardial application of saline or epicardial application of Lugol's solution. Ventricular fibrillation threshold was measured before and after each intervention by the single-stimulus technique. Application of Lugol's solution to the endocardium resulted in a 102 +/- 15% increase in ventricular fibrillation threshold from a control value of 26 +/- 2 to 53 +/- 6 mA (p less than .005). In two animals, ventricular fibrillation could not be initiated postoperatively. In the control groups, there were no significant changes in ventricular fibrillation threshold. Histologic examination revealed that Lugol's solution obliterated less than 0.5 mm of superficial endocardium while sparing the adjacent myocardium. Electrophysiologic and rheologic data confirmed the discrete nature of the chemical injury. Thus ablation of the superficial ventricular endocardium with Lugol's solution results in a profound increase in the ventricular fibrillation threshold with only minimal tissue destruction.
Left ventricular remodeling after myocardial infarction: a corollary to infarct expansion.
Authors: McKay R G , Pfeffer M A , Pasternak R C , Markis J E , Come P C , Nakao S , Alderman J D , Ferguson J J , Safian R D , Grossman W
Published: June 2011

Dilatation of infarcted segments (infarct expansion) may occur during recovery from myocardial infarction, but the fate of noninfarcted segments is uncertain. Accordingly, left ventricular geometric changes were assessed by left ventricular angiography and M mode echocardiography on admission and 2 weeks later in 30 patients with their first acute transmural myocardial infarction. All patients demonstrated chest pain, ST segment elevation with subsequent development of Q waves (15 anterior, 15 inferior), and elevation of cardiac enzymes. Sequential left ventricular angiographic and hemodynamic findings were available in these patients by virtue of their participation in a study of thrombolysis in acute myocardial infarction. By that study design, all patients treated successfully with thrombolytic therapy and demonstrating improvement of flow in an occluded coronary artery underwent repeat cardiac catheterization. At 2 weeks there was a significant decrease in left ventricular and pulmonary capillary wedge pressures (p less than .01), whereas both left ventricular end-diastolic (LVEDV) and end-systolic (LVESV) volume indexes increased (p less than .01). The increase in LVEDV correlated directly with the percentage of the ventriculographic silhouette that was akinetic or dyskinetic at the initial catheterization (r = .71, p less than .001). To assess regional changes in both infarcted and noninfarcted segments, serial endocardial perimeter lengths of both the akinetic-dyskinetic segments (infarction zone) and of the remainder of the cardiac silhouette (noninfarction zone) were measured in all patients who demonstrated at least a 20% increase in their LVEDV at 2 weeks after myocardial infarction. Notably, there was a mean increase of 13% in the endocardial perimeter length of infarcted segments and a 19% increase in the endocardial perimeter length of noninfarcted segments. Serial M mode echocardiographic studies showed no significant change in the wall thickness of noninfarcted myocardial segments. Hemodynamic changes that occurred in this subgroup of patients included significant decreases in left ventricular end-diastolic and pulmonary capillary wedge pressures (p less than .05) and significant increases in angiographic cardiac index (p less than .01) and LVESV index (p less than .01). We conclude that in patients who manifest cardiac dilatation in the early convalescent period after myocardial infarction, there is remodeling of the entire left ventricle including infarct expansion of akinetic-dyskinetic segments and volume-overload hypertrophy of noninfarcted segments.(ABSTRACT TRUNCATED AT 400 WORDS)
Preservation of glomerular filtration rate in human heart failure by activation of the renin-angiotensin system.
Authors: Packer M , Lee W H , Kessler P D
Published: June 2011

When renal perfusion pressure is reduced in experimentally induced low-output states, glomerular filtration rate is preserved by angiotensin II-mediated efferent arteriolar vasoconstriction, but available evidence in man suggests that angiotensin II supports renal function only to the extent that it preserves systemic blood pressure. We performed simultaneous assessments of cardiac and renal function in 56 patients with severe chronic heart failure before and after 1 to 3 months of converting-enzyme inhibition. Among the 29 patients with a pretreatment renal perfusion pressure under 70 mm Hg, patients with preserved renal function (creatinine clearance greater than 50 ml/min/1.73 m2) had markedly elevated values for plasma renin activity (11.8 +/- 3.8 ng/ml/hr) and showed a significant decline in creatinine clearance after converting-enzyme inhibition (61.1 +/- 3.0 to 45.9 +/- 5.3 ml/min/1.73 m2; p less than .05). In contrast, although similar with respect to all pretreatment demographic, hemodynamic, and clinical variables, patients with a creatinine clearance under 50 ml/min/1.73 m2 had low values for plasma renin activity (3.4 +/- 0.8 ng/ml/hr) and, despite similar drug-induced decreases in systemic blood pressure, showed no change in creatinine clearance after therapy with captopril or enalapril (32.6 +/- 2.5 to 41.4 +/- 3.8 ml/min/1.73 m2). Changes in creatinine clearance varied linearly and inversely with pretreatment values for plasma renin activity (r = - .64, p less than .001); converting-enzyme inhibition effectively abolished the pretreatment difference in renal function seen in the high- and low-renin subgroups. In the 27 patients with a renal perfusion pressure of 70 mm Hg or greater, creatinine clearance did not vary significantly with plasma renin activity and was not altered by therapy.(ABSTRACT TRUNCATED AT 250 WORDS)
The effects of doxorubicin on ventricular tachycardia.
Authors: le Marec H , Spinelli W , Rosen M R
Published: June 2011

Doxorubicin, in concentrations that have no effect on fast or slow response action potentials, has been shown to suppress ouabain-induced delayed afterdepolarizations. In this study, we used standard microelectrode techniques to determine the effects of doxorubicin on isolated canine Purkinje fibers. We studied automaticity induced at normal and low membrane potentials, conduction in normal and K+-depolarized Purkinje fibers, and triggered activity induced by ouabain and by experimental myocardial infarction. Doxorubicin, 50 microM, suppressed the triggered activity and the delayed afterdepolarizations that induced it, but had no effect on the other variables. We then studied the effects of intravenous doxorubicin, 16 to 64 mg/m2 body surface area, on ouabain-induced ventricular tachycardia and the ventricular tachycardia that occurs 24 hr after ligation of the left anterior descending coronary artery in the intact dog. There was no effect on the infarct-induced arrhythmia, but concentrations of doxorubicin that had no other effect on the electrocardiogram suppressed those ouabain-induced arrhythmias that appeared to have been triggered. The automatic arrhythmias induced by ouabain were not affected. Both the latter mechanisms were verified in studies of isolated Purkinje fibers that were obtained on completion of the intact animal experiments. These results indicate that agents having high selectivity for specific arrhythmogenic mechanisms can be useful adjuncts in discriminating among the mechanisms responsible for arrhythmias in intact animals.