bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of adenosine and adenine nucleotides on the atrioventricular node of isolated guinea pig hearts.
Authors: Belardinelli L , Shryock J , West G A , Clemo H F , DiMarco J P , Berne R M
Published: June 2011

The primary goal of this study was to determine whether the slowing of atrioventricular (AV) conduction by ATP is caused by ATP per se or is mediated by adenosine formed from ATP degradation. We assessed the effects of ATP, beta, gamma-methylene ATP, ADP, AMP, and adenosine on AV conduction time in the isolated perfused guinea pig heart. The cardiac effluent was collected and analyzed for its content of adenine nucleotides and nucleosides. Perfused ATP was rapidly and almost completely broken down to AMP and adenosine; only 2.5 +/- 0.5% of the infused ATP was recoverable in the effluent. A significant correlation was found between the effluent concentration of adenosine and atria-to-His bundle (A-H) conduction time. Compounds that altered the effect of adenosine on A-H conduction likewise altered the effect of ATP: (1) aminophylline, a competitive antagonist of adenosine, antagonized the ATP-induced A-H prolongation; (2) adenosine deaminase, the enzyme responsible for the deamination of adenosine to inosine, reduced the effect of ATP by 82%; (3) the adenosine transport blockers NBMPR and dipyridamole markedly enhanced the effect of ATP; and (4) EHNA, an inhibitor of adenosine deaminase, potentiated the effect of ATP. Furthermore, the less hydrolyzable ATP analog, beta, gamma-methylene ATP, was less potent than ATP in causing A-H prolongation. We conclude that the adenosine-like action of ATP on the guinea pig AV node requires that ATP first be degraded to adenosine.
Hemodynamic effects of dynamic exercise in children and adolescents with moderate-to-small ventricular septal defects.
Authors: Bendien C , Bossina K K , Buurma A E , Gerding A M , Kuipers J R , Landsman M L , Mook G A , Zijlstra W G
Published: June 2011

We studied the hemodynamic effects of dynamic exercise during cardiac catheterization in 35 children and adolescents with small-to-moderate ventricular septal defects. Eighteen of them exercised at 25% and 50% of their maximum workload and 17 exercised at 60%. There was no significant difference between the two groups with respect to age and body mass, height, and surface area. The changes evoked by exercise showed the same pattern at the different workloads, although they were more marked at the higher than at the lower percentage of maximum workload. During exercise the pulmonary vascular resistance did not change, in contrast to the systemic vascular resistance, which decreased. The pulmonary and systemic blood flows both increased, while the left-to-right shunt flow did not change, which led to a decrease of the left-to-right shunt fraction. As the heart rate increased and the shunt flow did not change, the shunt volume per beat decreased during exercise. We conclude that in patients with small-to-moderate ventricular septal defects the hemodynamic effects of dynamic exercise are favorable because the normal rise in systemic blood flow occurs without a corresponding increase in left-to-right shunt flow. Consequently, children and adolescents with such defects should not be restricted in their dynamic exercise activities.
Alteration of diastolic filling rate during exercise radionuclide angiography: a highly sensitive technique for detection of coronary artery disease.
Authors: Poliner L R , Farber S H , Glaeser D H , Nylaan L , Verani M S , Roberts R
Published: June 2011

Diastolic and systolic parameters of left ventricular performance were characterized from high-frequency time-activity curves obtained in 10 normal volunteers (mean age 29 +/- 4 yr), in 25 patients with normal coronary arteries, and in 50 patients with coronary artery disease (CAD) at rest and during three stages of exercise radionuclide angiography. In the normal volunteers ejection fraction was 65 +/- 5% (SD) at rest and 78 +/- 5% with exercise (p less than .001). In patients with normal coronary arteries ejection fraction was 64 +/- 5% at rest and 72 +/- 8% with exercise (p less than .0001). In patients with CAD resting ejection fraction was 60 +/- 10% and that during exercise was 61 +/- 13% (p = NS). Peak diastolic filling rate in the first half of diastole, peak systolic ejection rate, and times to peak rates and to end-systole were measured. In the normal subjects resting peak diastolic filling rate was 3.1 +/- 0.6 end-diastolic counts/sec and it increased in all subjects with exercise to 3.6 +/- 0.7 (p less than .05). In patients with normal arteries and those with CAD peak diastolic filling rate was 2.3 +/- 0.8 at rest and with exercise this parameter increased to 3.2 +/- 1.1 (p less than .001) in patients with normal arteries and fell to 1.7 +/- 0.6 in those with CAD (p less than .001). Peak systolic ejection rate decreased from 2.5 +/- 0.8 to 1.9 +/- 0.8 with exercise in patients with CAD (p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)
Termination of paroxysmal supraventricular tachycardia with a single oral dose of diltiazem and propranolol.
Authors: Yeh S J , Lin F C , Chou Y Y , Hung J S , Wu D
Published: June 2011

The efficacy of a single oral dose combination of 120 mg diltiazem and 160 mg propranolol in terminating paroxysmal supraventricular tachycardia (PSVT) was evaluated in 15 patients. All 15 patients underwent electrical induction of PSVT that lasted longer than 15 min, and all underwent randomized crossover placebo and diltiazem and propranolol studies on 2 consecutive days. On each day PSVT was induced and placebo or diltiazem and propranolol was administered 15 min later. Electrical conversion of PSVT was performed when severe symptoms occurred or at the end of 240 min. With placebo PSVT lasted 164 +/- 89 (mean +/- SD) min; four patients had spontaneous conversion. With diltiazem and propranolol PSVT lasted 39 +/- 49 min (p less than .001); 14 patients had spontaneous conversion in an average of 27 +/- 15 min. None of the 14 patients had electrical reinduction of sustained PSVT after conversion. The sinus nodal recovery time during spontaneous or electrical conversion of PSVT was 911 +/- 459 msec with placebo and 1076 +/- 270 msec with diltiazem and propranolol (NS). Two patients developed transient second-degree atrioventricular block and junctional rhythm while on diltiazem and propranolol. Serum diltiazem and propranolol levels (ng/ml) after diltiazem and propranolol in five patients were, respectively, 49 +/- 26 and 108 +/- 101 at 15 min, 232 +/- 147 and 228 +/- 148 at 30 min, 254 +/- 169 and 370 +/- 393 at 45 min, 280 +/- 115 and 209 +/- 189 at 60 min, 188 +/- 72 and 268 +/- 264 at 120 min, and 118 +/- 57 and 265 +/- 148 at 240 min.(ABSTRACT TRUNCATED AT 250 WORDS)
Digitalis-induced augmentation of cardiopulmonary baroreflex control of forearm vascular resistance.
Authors: Imamura T , Takeshita A , Ashihara T , Yamamoto K , Hoka S , Nakamura M
Published: June 2011

We sought to determine whether digitalis augments cardiopulmonary baroreflex control of forearm vascular resistance in normal young men. Cardiopulmonary baroreceptor input was reduced with lower body negative pressure (LBNP) at 10 and 20 mm Hg, which decreased central venous pressure but did not alter blood pressure or heart rate. Decreases in forearm blood flow and increases in forearm vascular resistance with LBNP were greater after administration of lanatoside C (Cedilanid) than before, and the slope of the regression line relating changes in central venous pressure and those in forearm vascular resistance was steeper after lanatoside C. Vasoconstrictor responses to the cold pressor test did not differ before and after lanatoside C, which suggested that augmented responses to LBNP after the drug were not caused by a generalized change in reflex control. These results suggest that lanatoside C augments the tonic inhibitory influence of cardiopulmonary baroreceptors in normal men.
The hemodynamic effects of cardiac tamponade: mainly the result of atrial, not ventricular, compression.
Authors: Fowler N O , Gabel M
Published: June 2011

We studied the hemodynamic effects of surgically induced regional cardiac tamponade in anesthetized dogs. Tamponade restricted to either the right or the left ventricle was compared with tamponade of either ventricle and both atria. Intrapericardial pressures were elevated to approximately 20 mm Hg. With tamponade of the right ventricle alone, aortic pressure rose from 161 +/- 3.8 to 164 +/- 3.4 mm Hg (p greater than .05) and cardiac output fell from 149.4 +/- 16.1 to 134.9 +/- 11.9 ml/kg/min (p greater than .05). However, tamponade of the right ventricle plus both atria decreased mean aortic pressure from 152.5 +/- 3.6 to 115.9 +/- 8.7 mm Hg (p less than .01) and cardiac output fell from 118 +/- 14.8 to 38.9 +/- 4.8 ml/kg/min (p less than .01). With tamponade of the left ventricle alone, aortic mean pressure changed significantly from 158.5 +/- 6.1 (control) to 148.9 +/- 5.0 mm Hg (tamponade) (p less than .05) and cardiac output was 135.5 +/- 28.3 (control) and 111 +/- 24.7 ml/kg/min (tamponade) (p greater than .05). However, when the atria were included, mean aortic pressure fell significantly more from 155.5 +/- 5.4 to 105.5 +/- 10.4 mm Hg (p less than .01) and cardiac output fell from 142.2 +/- 16 to 47.8 +/- 6.4 ml/kg/min (p less than .01). Atrial pressure rose when the atria were included, but not with tamponade of the left ventricle alone. Right but not left atrial pressure rose slightly with isolated right ventricular tamponade. We conclude that the principal hemodynamic effects of cardiac tamponade are not the result of compression of either the right or the left ventricle, but are the consequence of compression of the atria and/or the venae cavae and the pulmonary veins.
Treatment of hypertension and its effect on cardiovascular risk factors: data from the Framingham Heart Study.
Authors: Shea S , Cook E F , Kannel W B , Goldman L
Published: June 2011

Analysis of the Framingham Heart Study experience between 1958 and 1970 showed a progressive increase in the rate of treatment and control of hypertension. With cross-sectional criteria to define diastolic hypertension, the treatment rate rose from 35% in 1958 through 1960 to 69% in 1968 through 1970 (p less than .001), and the treatment rate for sustained hypertension rose from 55% in 1958 through 1960 to 85% in 1968 through 1970 (p less than .001). Treated hypertensive subjects had higher pretreatment values of blood pressure but not of other cardiovascular risk factors than untreated hypertensive subjects. Treatment was more successful in controlling hypertension in later years (p less than .001), but in all years treatment reduced systolic and diastolic blood pressure without causing significant changes in mean serum cholesterol or glucose levels. In treated hypertensive subjects, the 8 year predicted risk of coronary heart disease declined by 2.3 events per 100 people compared with that in untreated hypertensive subjects (p less than .0001). The observed incidence of coronary heart disease was consistent with these predictions and suggested that treatment may be especially beneficial in subjects who have systolic blood pressures of 180 mm Hg or higher and who are treated for more than 2 successive years.
Apical hypertrophic cardiomyopathy: evaluation by noninvasive and invasive techniques in 23 patients.
Authors: Keren G , Belhassen B , Sherez J , Miller H I , Megidish R , Berenfeld D , Laniado S
Published: June 2011

Over a 3 year period we evaluated 23 patients (16 men, seven women) with apical hypertrophic cardiomyopathy by noninvasive and invasive methods. Sixteen patients had chest pain. In 17, results of cardiovascular examination were normal. The electrocardiogram showed precordial inverted T waves in all patients and these were of mild-to-moderate amplitude (less than 10 mm) in 18 and giant (greater than 10 mm) in five. M mode echocardiography revealed a typical pattern of contraction and relaxation in the apical region of the left ventricle that was associated with significant hypertrophy. These findings were confirmed by two-dimensional echocardiography. Systolic anterior motion of the mitral valve was not observed nor was there any evidence of obstruction of the left ventricular outflow tract. Results of Doppler echocardiographic study of the mitral and aortic flow were normal in all patients but one who had mild mitral insufficiency. Radionuclide studies of 14 patients revealed a mean left ventricular ejection fraction of 66 +/- 6% (range 55% to 79%), with normal left ventricular contraction in all patients but two with apical hypokinesis. In all six patients who underwent catheterization a characteristic appearance of the left ventricle at end-systole as well as abnormal end-diastolic contour were noted on the left ventricular angiogram, but the "ace of spades" configuration was seen in only one. We conclude that the 23 patients studied form a homogeneous group of individuals with nonobstructive apical hypertrophic cardiomyopathy, which differs in many respects from cardiomyopathies reported by other investigators.
Sex differences in early and long-term results of coronary angioplasty in the NHLBI PTCA Registry.
Authors: Cowley M J , Mullin S M , Kelsey S F , Kent K M , Gruentzig A R , Detre K M , Passamani E R
Published: June 2011

To assess whether gender influenced the outcome of percutaneous transluminal coronary angioplasty (PTCA), we analyzed data from the NHLBI PTCA Registry. Early results were compared in 705 women and 2374 men. Women were older (p less than .01) and had more unstable angina (p less than .01), and class 3 or 4 angina (p less than .01). Men had more multivessel disease (p less than .01), prior bypass surgery (p less than .01), and abnormal left ventricular function (p less than .05). Women had a lower angiographic success rate (60.3 vs 66.2%; p less than .01) and had a lower clinical success rate (56.6% vs 62.2%; p less than .01). More women had complications (27.2% vs 19.4%; p less than .01), but overall frequency of major complications (death, myocardial infarction, emergency surgery) was not different (9.8% vs 9.3%). Women had a higher incidence of coronary dissection (p less than .05) and higher in-hospital mortality (1.8% vs 0.7%; p less than .01). PTCA-related mortality was nearly six times higher in women (1.7% vs 0.3%; p less than .001) and mortality with emergency surgery was more than five time higher (17.4% vs 3.2%; p less than .001). Multivariate analysis indicated that female gender was an independent predictor for lower success (p less than .05) and early mortality (p less than .05) and was the only baseline predictor for PTCA-related mortality.(ABSTRACT TRUNCATED AT 250 WORDS)
Asynchronous left ventricular regional function and impaired global diastolic filling in patients with coronary artery disease: reversal after coronary angioplasty.
Authors: Bonow R O , Vitale D F , Bacharach S L , Frederick T M , Kent K M , Green M V
Published: June 2011

Left ventricular diastolic filling is impaired in many patients with coronary artery disease and normal left ventricular systolic function, and is improved in many patients after coronary angioplasty (PTCA). To investigate the mechanisms for this improvement, we studied regional asynchrony by radionuclide angiography in 26 patients with single-vessel coronary artery disease before and after successful PTCA. Before PTCA, all patients had normal ejection fractions at rest and normal qualitative left ventricular regional wall motion, as determined by radionuclide and contrast angiography. Quantitative left ventricular regional function was assessed by dividing the left ventricular region of interest into 20 sectors. Phase analysis was performed on each sector's time-activity curve, and the average intersector phase difference was used as an index of left ventricular regional synchrony. Before PTCA, average intersector phase difference was increased compared with normal (6.0 +/- 2.2 vs 4.0 +/- 1.7 degrees, p less than .005), indicating asynchronous regional function. After PTCA, ejection fraction at rest was unchanged, but peak left ventricular filling rate at rest increased from 2.5 +/- 0.6 to 3.0 +/- 0.6 end-diastolic volume/sec (p less than .001) and was associated with a decrease in average intersector phase difference from 6.0 +/- 2.2 to 5.1 +/- 2.3 degrees (p less than .05). Average intersector phase difference decreased in 16 of 21 patients in whom peak filling rate increased after PTCA (p less than .005), compared with one of five patients in whom peak filling rate was unchanged or decreased. Hence, improved global left ventricular filling after PTCA was associated with more synchronous left ventricular regional behavior. To identify the cause of regional asynchrony before PTCA, we then generated time-activity curves from each of four left ventricular quadrants. These data indicated that the asynchrony was caused by regional variation in timing of diastolic rather than systolic events and that PTCA resulted in reduction in regional diastolic asynchrony. These data suggest that in many patients with coronary artery disease and normal left ventricular systolic function, impaired global diastolic filling may result from asynchronous left ventricular regional diastolic function, which is a reversible manifestation of myocardial ischemia or reduced coronary flow.
Inotropic therapy for refractory congestive heart failure with oral fenoximone (MDL-17,043): poor long-term results despite early hemodynamic and clinical improvement.
Authors: Shah P K , Amin D K , Hulse S , Shellock F , Swan H J
Published: June 2011

Thirteen male patients with NYHA class IV congestive heart failure refractory to conventional therapy were treated with oral fenoximone, a new imidazole compound with inotropic and vasodilator effects, for a mean duration of 11 weeks (range 2 to 34). On initial hemodynamic evaluation, the effects of oral fenoximone were comparable to those of the intravenous form and included a significant (p = .0001) increase in cardiac index (mean +/- SD) (1.7 +/- 0.4 to 3.0 +/- 0.7 liters/min/m2) and a significant (p = .0001) but modest decrease in pulmonary capillary wedge pressure (27 +/- 6 to 23 +/- 6 mm Hg), with only minor overall changes in heart rate and arterial blood pressure. Symptomatic improvement by at least one NYHA class was observed in all patients during the first week of therapy with fenoximone; however, severe and symptomatic congestive heart failure recurred in seven patients within an average of 8 weeks after initiation of therapy, resulting in death in all seven. Of the remaining six patients, two died suddenly at home within 3 weeks of initiation of therapy, one died from ventricular fibrillation in the hospital 7 weeks after initiation of therapy, and two died from noncardiac causes. One patient is currently alive with NYHA class II heart failure 21 weeks after the initiation of therapy. Partial or complete attenuation of hemodynamic efficacy of oral fenoximone during long-term administration was demonstrated during repeat hemodynamic evaluation in six of eight patients. We conclude that despite short-term hemodynamic and clinical benefits, oral fenoximone therapy in patients with NYHA class IV congestive heart failure does not produce sustained clinical or hemodynamic benefit and is associated with a high mortality.
Autotransplantation of skeletal muscle into myocardium.
Authors: Sola O M , Dillard D H , Ivey T D , Haneda K , Itoh T , Thomas R
Published: June 2011

In a series of 15 studies in dogs, sternocleidomastoid muscle was used to replace deficits created in left ventricular myocardium and sternohyoid muscle was used to replace portions of right myocardial wall. The five right ventricular autotransplants resulted in a 100% surgical success rate, with animals electively killed between 3 and 55 weeks after surgery. In 10 left ventricular studies excision of areas varying from 12 X 46 mm to 30 X 60 mm and incisions of from 40 mm to 70 mm in length were performed. Left ventricular studies resulted in a 60% surgical success rate, with clinically healthy animals being killed for study between 2 weeks and 50 weeks after surgery. Animals surviving the critical surgical recovery period showed no loss of weight or changes in activity. Gross findings at autopsy confirmed the viability of the skeletal muscle transplants. Borders were well healed and the grafted tissue was pliable. Histologic studies suggest that revascularization of skeletal muscle occurred from the myocardial side, and that there were healthy myocardial and skeletal muscle fibers at the junction, with evidence of regeneration.
Inhibition by diphosphonate compounds of calcification of porcine bioprosthetic heart valve cusps implanted subcutaneously in rats.
Authors: Levy R J , Hawley M A , Schoen F J , Lund S A , Liu P Y
Published: June 2011

Calcification limits the long-term success of heart valve bioprostheses fabricated from glutaraldehyde cross-linked porcine aortic valves. The pathophysiology of calcification of bioprostheses has been studied experimentally with subcutaneous implants of the valve cusps in rats; in this preparation, the accumulation of calcific deposits is biochemically and morphologically identical to that occurring in clinical specimens. The objective of the present study was to determine whether mineralization of bioprosthetic valve cusps (BC) subcutaneously implanted in 3-week-old male rats could be inhibited through the use of diphosphonate compounds. Ethanehydroxydiphosphonate (EHDP), administered by daily subcutaneous injection (25 mg/kg/24 hr) for 21 days inhibited calcification (BC Ca++ = 154.9 +/- 4.1), but caused somatic growth retardation and disruption of epiphyseal development. However, local administration of EHDP by osmotic pump (5 mg/kg/24 hr) implanted in direct contact with the cuspal tissue for 14 days prevented BC calcification (BC CA++ = 4.3 +/- 0.7) without adverse effects. Furthermore, EHDP given by osmotic pump had a prolonged effect on reducing calcification, as demonstrated by implants harvested 21 days (BC CA++ = 12.2 +/- 6.4) after the drug supply was exhausted. Finally, BC preincubated in aminopropanehydroxydiphosphonate for 24 hr before 21 day implantation underwent less calcification (CA++ = 24.2 +/- 7.4) than control valves (BC CA++ 126.6 +/- 7.5) with no adverse effects. We conclude that diphosphonates inhibit BC calcification, and that adverse effects of systemic therapy can be avoided by local administration.
Alternating contractility in pulsus alternans studied in the isolated canine heart.
Authors: McGaughey M D , Maughan W L , Sunagawa K , Sagawa K
Published: June 2011

We examined pulsus alternans in seven isolated, perfused canine left ventricles ejecting into a simulated arterial impedance. Left ventricular pressure-volume loops were measured during pulsus alternans while filing-source pressure was lowered. In all cases two distinct linear end-systolic pressure-volume relationships (ESPVRs) were noted for the strong and weak beats. The slopes of the ESPVRs of the strong beats were significantly greater than those of the weak beats (mean difference 0.9 +/- 0.6 mm Hg/ml, p less than .01), while the intercepts were not significantly different (mean difference 0.06 +/- 0.5 ml). Diastolic pressure-volume relationships for the strong and weak beats were not significantly different, excluding incomplete relaxation as a cause of pulsus alternans. Although the weak beats had both a smaller preceding end-diastolic volume and a larger end-systolic volume, the presence of two distinct ESPVRS for the strong and weak beats shows there is alternating ventricular chamber contractility in pulsus alternans that is not solely due to the Starling mechanism. The magnitude of alternation in pump function parameters such as pressure and stroke volume during pulsus alternans reflects the complex interactions of alternating contractile state with alternations in preload and afterload.
Laser recanalization of occluded atherosclerotic arteries in vivo and in vitro.
Authors: Abela G S , Normann S J , Cohen D M , Franzini D , Feldman R L , Crea F , Fenech A , Pepine C J , Conti C R
Published: June 2011

Controlled laser irradiation was used to recanalize atherosclerotic stenoses in vivo and in vitro. In 15 rabbits with atherosclerotic arteries a catheter was positioned in the distal aorta for angiographic examination and as a guide for a small silica optical fiber. Both Nd-YAG and argon lasers were used for recanalization with varying power and duration. As determined by angiographic studies the severity of iliofemoral stenoses in eight 15 arteries decreased from 78 +/- 18% to 32 +/- 11% (mean +/- SD). In one additional artery the stenosis improved from 45% to 25%, but this was associated with perforation. The other six arteries were perforated (two after fiber manipulation, four after laser discharge) without obvious improvement in severity of stenosis. No angiographic loss of distal circulation was noted. To better define tissue- laser interactions in the live-rabbits, lasing of 15 totally occluded atherosclerotic rabbit arterial segments in vitro was done while the optical fiber was advanced or fixed. When the fiber was fixed, serial sections showed that the new lumen was flame shaped. The width and depth of the lumen increased with increasing laser energy. When the fiber was advanced, histologic examination showed a smooth cylindrical vascular channel with limited lateral tissue damage. This study demonstrated that lasers can recanalize atherosclerotic stenoses in a live animal preparation; however, arterial perforation remains a problem.
Endogenous biosynthesis of prostacyclin during cardiac catheterization and angiography in man.
Authors: Roy L , Knapp H R , Robertson R M , FitzGerald G A
Published: June 2011

The potent platelet inhibitory and vasodilator properties of prostacyclin suggest that levels of this substance may be of relevance to drug action and pathologic processes in the coronary vascular bed. Attempts to estimate the coronary secretion rate of prostacyclin have relied on measurements of metabolites obtained via cardiac catheter, usually as an adjunct to coronary angiography. To test the hypothesis that such procedures might themselves perturb endogenous biosynthesis of prostacyclin we used mass spectrometry to measure plasma levels of 6-keto-prostaglandin (PG) F1 alpha across the coronary vascular bed, as well as to assess the excretion of a major urinary metabolite, 2,3-dinor-6-keto-PGF1 alpha (PGI-M), in patients undergoing cardiac catheterization. PGI-M excretion increased variably from a median 100 to 205 pg/mg creatinine (p less than .01) during catheterization with angiography and remained elevated 2 to 4 hr after initiation of the procedure. However, cardiac catheterization without angiography also stimulated metabolite excretion, perhaps reflecting catheter-induced vascular trauma. The direct effect of radiocontrast media on vascular release of prostacyclin was indicated by increased PGI-M excretion in healthy volunteers administered intravenous radiocontrast and by studies of the canine coronary artery and jugular vein in vitro. Measurement of plasma 6-keto-PGF1 alpha after left heart catheterization showed that levels in aortic (21 +/- 8 pg/ml) and coronary sinus (14 +/- 2 pg/ml) blood were increased compared with peripheral venous levels (less than or equal to 4 + 1 pg/ml) determined before this procedure.(ABSTRACT TRUNCATED AT 250 WORDS)
Associations of resting heart rate with concentrations of lipoprotein subfractions in sedentary men.
Authors: Williams P T , Haskell W L , Vranizan K M , Blair S N , Krauss R M , Superko H R , Albers J J , Frey-Hewitt B , Wood P D
Published: June 2011

In major prospective studies it has been reported that high heart rate at rest predicts the development of coronary heart disease (CHD) or cardiovascular disease (CVD) in men, but the mechanisms producing these relationships are unknown. Since lipoprotein levels contribute strongly to the risk of CHD and CVD, we examined the relationship of resting heart rate to plasma concentrations of high-density (HDL), low-density (LDL), and very low-density (VLDL) lipoproteins, apolipoprotein (apo) A-I and A-II, and serum concentrations of lipoprotein subfractions in 81 men to determine if atherogenic lipoproteins could potentially induce the reported association of heart rate with development of CHD or CVD. The significant (p less than or equal to .05) Spearman's correlations for resting heart rate vs HDL2 mass (rs = -.24), HDL3 mass (rs = -.40), HDL cholesterol (rs = -.36), apo A-I (rs = -.29), triglycerides (rs = .31), VLDL cholesterol (rs = .24), VLDL mass (rs = .27), and LDL mass of Sof 0-7 subfraction (rs = .30) lend support to our hypothesis of lipoprotein-induced relationships of CHD with heart rate. The correlations for resting heart rate vs triglycerides, HDL cholesterol, HDL3 mass, VLDL mass, and LDL mass of Sof 0-7 subfraction remain significant when adjusted for adiposity, age, smoking habits, diet, and physical fitness as measured by maximum aerobic power (VO2 max) or submaximal heart rate during a graded exercise test.
Concentration-dependent enhancement of junctional pacemaker activity by verapamil in man.
Authors: Schwartz J B , Nielsen A P , Griffin J C
Published: June 2011

The effects of verapamil on junctional and sinoatrial activity were studied in eight patients with third-degree atrioventricular block and stable junctional rhythms. After intravenous infusion of verapamil three steady-state levels were reached as follows: 34 +/- 16 (SS1), 68 +/- 30 (SS2), and 129 +/- 54 (SS3) ng/ml. At each steady-state level, spontaneous sinus and junctional cycle lengths, QT intervals, junctional recovery times after ventricular pacing, blood pressure, and circulating catecholamine concentrations were measured. These measurements were compared with observations made during an identical protocol (except for the exclusion of verapamil infusions) on a control day. No significant changes were detected in the spontaneous sinus or junctional cycle length, junctional recovery times at a fixed pacing cycle length, blood pressure, or circulating catecholamine concentrations during the control day. In response to verapamil, the mean junctional cycle length decreased from a baseline value of 1320 +/- 239 to 1254 +/- 210, 1199 +/- 214, 1069 +/- 151 msec at SS1, SS2, and SS3 (p less than .01). Sinus cycle length (msec) was unaffected or slightly lengthened from 749 +/- 165 at baseline to 821 +/- 222 at SS1, 831 +/- 222 at SS2, and 817 +/- 175 at SS3 (NS). Mean blood pressure, circulating catecholamine concentrations, and corrected QT intervals were also unchanged by verapamil. Verapamil enhanced junctional pacemaker activity in patients with third-degree atrioventricular block, suggesting that (1) these rhythms originate in cells that are not suppressed by the slow-channel antagonism of verapamil and (2) the acceleration of junctional activity seen in response to verapamil reflects a verapamil effect rather than toxicity.
Noninvasive study of left ventricular performance in obese patients: influence of duration of obesity.
Authors: Nakajima T , Fujioka S , Tokunaga K , Hirobe K , Matsuzawa Y , Tarui S
Published: June 2011

We studied the performance of the left ventricle in 35 obese patients by means of noninvasive methods, including echocardiography, carotid arterial pulse tracing, and phonocardiography. Patients were divided into two groups according to the duration of obesity: group 1 included patients who had been obese for less than 15 years, and group 2 comprised patients who had been obese for more than 15 years. There were no differences in the degree of obesity and cellularity of adipose tissue between two groups. Left ventricular dimension and wall thickness, stroke volume, and cardiac output were significantly greater in both groups of obese patients than in nonobese control subjects. Group 2 had a significantly increased end-diastolic dimension index (DdI, calculated as end-diastolic dimension/cube root of body surface area), stroke index (SI), and radius/wall thickness ratio (R/Th) of the left ventricle compared with group 1. Multiple regression analysis showed that DdI, SI, and R/Th correlated significantly with the duration of obesity. We conclude that alterations of cardiac performance in obese patients with left ventricular enlargement and wall thickening is attributed not only to the excess of body weight but also to the duration of obesity.
Relationship of the lytic state to successful reperfusion with standard- and low-dose intracoronary streptokinase.
Authors: Rothbard R L , Fitzpatrick P G , Francis C W , Caton D M , Hood W B , Marder V J
Published: June 2011

The influence of a systemic lytic state on reperfusion obtained after intracoronary streptokinase (SK) therapy has been evaluated in 15 patients with acute myocardial infarction and complete coronary occlusion. Coronary angiographic studies and measurements of blood fibrinolytic parameters were repeated at 15 min intervals during the infusion of a standard dose of SK and were compared with the results with approximately one-tenth the standard dose. Successful reperfusion was obtained in only 20% (2/10) of patients receiving the low dose, compared with a 75% to 80% success rate in patients receiving the standard dose as initial treatment (4/5) or as follow-up treatment of patients in whom low-dose therapy failed (6/8). There was a striking association between reperfusion and development of the lytic state in that all 12 treatments resulting in reperfusion also caused a lytic state and all seven treatments that failed to produce a lytic state also failed to induce reperfusion (p less than .001). Among the successfully treated patients, the dose of SK that induced a lytic state was relatively constant. However, coronary arterial thrombi differed in susceptibility to treatment. Sensitive thrombi (5/12) dissolved before the lytic state occurred and at a lower SK dose than that needed to cause a lytic state; more resistant thrombi (7/12) required a longer time and a significantly larger SK dose to dissolve. These results indicate that intrinsic properties of the thrombus influence the rate and outcome of treatment and that a minimal dose of SK (about 200,000 U) is required to ensure lasting reperfusion in susceptible patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Early loss of postextrasystolic potentiation in acutely ischemic myocardium: evaluation by contrast two-dimensional echocardiography.
Authors: Force T , Kemper A J , Cohen C , Parisi A F
Published: June 2011

Studies in animals with acutely ischemic hearts have suggested that postextrasystolic potentiation (PESP) may predict the viability of dysfunctional myocardium. Most of these data have been obtained with sonomicrometers and therefore the presence and extent of PESP throughout the entire region at risk has not been defined. In this study we used contrast two-dimensional echocardiography (2DE) to define region at risk in vivo, and then with quantitative 2DE we examined the proportion of the region at risk that demonstrated PESP, the degree of the potentiation, and the time course of this response. The region at risk was divided into a central (inner 50%) and two peripheral (25% each) ischemic zones. Adjacent contrast-enhanced myocardium was divided into near and far border zones that were equal in size to the adjacent peripheral ischemic zone. Systolic thickening was analyzed within each zone along multiple radii at 5, 30, and 120 min after coronary occlusion. PESP was absent in the central ischemic zone at all three times. In the peripheral ischemic zone at 5 min, a small amount of PESP was detected (-4.1% vs + 3.1% for nonpotentiated and potentiated thickening, respectively; p less than .01). At 30 min after occlusion, no potentiation was seen in the region at risk and PESP was confined to the contrast-enhanced near and far border zones. These findings persisted at 120 min. These data indicate that the response to PESP is localized to perfused myocardium by 30 min after acute occlusion. PESP is therefore of limited value in predicting the presence of ischemic, potentially viable myocardium early in the course of acute infarction.
Serum potassium concentration as a risk factor of ventricular arrhythmias early in acute myocardial infarction.
Authors: Nordrehaug J E , Johannessen K A , von der Lippe G
Published: June 2011

Sixty patients with a first acute myocardial infarction and no current treatment with cardioactive drugs were included in a prospective study of the relationship between serum potassium concentration and the early occurrence of ventricular tachycardia and premature ventricular contractions (PVCs). Serum potassium level (range 2.5 to 5 mmol/liter) was estimated 3.8 +/- 2.5 hr (mean +/- SD) after the onset of the infarction, and Holter monitoring was performed during the subsequent 12 hr. In multivariate analysis, serum potassium level was negatively and age positively related to ventricular tachycardia. Among the subclasses of PVCs (frequent unifocal, multifocal, couplets, bigeminy), serum potassium concentration was negatively related to the frequent unifocal subclass; hypertension was related to couplets and to the presence of any of the subclasses, and serum aspartate aminotransferase concentration was related to multifocal PVCs. Heart failure leading to death was related to all subclasses of PVC. Serum potassium concentration is an independent inverse predictor of the occurrence of ventricular tachycardia and frequent unifocal PVCs early in acute myocardial infarction.
Adaptation to the stress of tachycardia in patients with coronary artery disease: insight into the mechanism of the warm-up phenomenon.
Authors: Williams D O , Bass T A , Gewirtz H , Most A S
Published: June 2011

Adaptation to exercise or the "warm up phenomenon" has been observed in some patients with angina pectoris. To investigate adaptation, eleven patients with exertional angina pectoris and angiographic evidence of coronary artery disease underwent two identical bouts of sequential tachycardia stress separated by a brief recovery period. Manifestations of ischemia were less during the second stress, as evidenced by a reduction in the severity of angina pectoris, less ST segment depression, and improved lactate extraction. Peak coronary blood flow during the second stress (81 +/- 20 ml/min) was not significantly different from that during the first (95 +/- 32 ml/min). Regional myocardial oxygen consumption, however, was significantly (p = .03) lower during the second stress (8.8 +/- 2.4 ml O2/min) when compared with the first (11.4 +/- 3.0 ml O2/min). Thus, patients with coronary artery disease can develop anginal tolerance to the stress of tachycardia similar to that observed after repeated bouts of exercise. A relative reduction in myocardial oxygen consumption, rather than an increase in coronary blood flow, appears to account for this phenomenon.
Angiographic findings after myocardial infarction in patients with previous bypass surgery: explanations for smaller infarcts in this group compared with control patients.
Authors: Crean P A , Waters D D , Bosch X , Pelletier G B , Roy D , Théroux P
Published: June 2011

The incidence of previous coronary artery bypass surgery (CABS) in patients with acute myocardial infarction admitted to our hospital has risen from 2.3% to 11.2% in 6 years. We compared infarct size and the angiographically determined cause of infarction in 52 control patients and in 52 consecutive patients with acute myocardial infarction at least 2 months after they had undergone CABS. Baseline characteristics were similar in both groups except for a higher incidence of preexisting Q waves in the post-CABS group (22 vs 10; p less than .05). Indexes of myocardial infarct size were smaller in the post-CABS group compared with those in control patients: peak creatine kinease (CK) level (IU/liter) 1113 +/- 1094 (mean +/- SD) vs 1824 +/- 1932 (p less than .01), peak CK-MB level (IU/liter) 173 +/- 230 vs 272 +/- 332 (p less than .02), peak summed ST segment elevation (mm) 3.5 +/- 4.8 vs 8.2 +/- 9.9 (p less than .005), and QRS score on days 7 to 10, 1.9 +/- 3.0 vs 4.3 +/- 3.4 (p less than .001). Postinfarction left ventricular ejection fraction was higher in the post-CABS group (53 +/- 13%) compared with that in control patients (47 +/- 12%; p less than .05). The incidence of total occlusion of the artery to the infarct zone was similar in the post-CABS and control patients (33 vs 27), as was the incidence of one-, two-, and three-vessel disease (artery plus graft). Collateral blood flow to the infarct zone was found in 27 post-CABS patients and in 23 control patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Myocardial perfusion after aortocoronary bypass surgery: measurements at rest and after administration of isoproterenol.
Authors: Schmidt D H , Blau F M , Hendrix L J , Kamath M L , Ray G
Published: June 2011

This study examined quantitative regional myocardial perfusion (RMP) measured by the washout of 133Xe at rest and after an isoproterenol challenge in 50 patients (group I) studied 8 to 14 days after they underwent saphenous vein bypass grafting to the left coronary artery, and compared this with RMP measured in the native left coronary artery in 14 patients (group II) with significant coronary artery disease and in 12 normal subjects (group III). The double product of the heart rate and aortic systolic pressure was used as an indicator of demand. The statistical significance of group comparisons was analyzed with Dunn's multiple comparisons among means test. Analysis of the data showed no significant difference among the groups with respect to aortic systolic pressure. In subjects at rest, heart rate was lower in groups II and III than in group I, and double product was lower in group II than in group I. After isoproterenol, both heart rate and double product were lower in group II compared with groups I and III, but there was no significant difference between groups I and III with respect to heart rate or double product. Mean resting RMP in group II was lower than in group I; however, results of other group comparisons were insignificant for resting parameters. After isoproterenol, mean flow (ml/100 g/min) in group I was similar to flow in group III (130 +/- 24 vs 139 +/- 26). In contrast, the average flow response after isoproterenol was significantly less in group II when compared with that in group I (105 +/- 20 vs 130 +/- 24) and with that in group III (105 +/- 20 vs 139 +/- 26). Because of differences in levels of demand with isoproterenol, the change in flow was normalized to the percent increase in double product. These data showed results similar to those above, i.e., normalized RMP in patients with coronary artery disease was significantly lower than that in normal subjects (82 +/- 41 vs 119 +/- 57) and in revascularized patients (82 +/- 41 vs 105 +/- 54). However, there was no significant difference between normal subjects and patients who had undergone surgery. To further evaluate the relationship of flow response to demand parameters, we plotted RMP/double product vs resistance. The data revealed a significant correlation between these variables in all groups both in subjects at rest and after isoproterenol.(ABSTRACT TRUNCATED AT 400 WORDS)
The effects of single premature stimuli on automatic and triggered rhythms in isolated canine Purkinje fibers.
Authors: Dangman K H , Hoffman B F
Published: June 2011

We studied the effects of single premature stimuli on automatic and triggered rhythms occurring in preparations of isolated canine Purkinje fibers. Preparations were made from false tendons, the subendocardial right bundle branch, and infarct zone Purkinje fibers 24 hr after occlusion of the left anterior descending coronary artery, and were studied by standard microelectrode techniques. Single premature impulses almost always produced reset of automatic rhythms, whether the pacemaker had a low (less than -60 mV), intermediate (-61 to -70 mV), or high (greater than -70 mV) maximum diastolic potential. In contrast, single premature impulses imposed on triggered rhythms sometimes were found to alter these rhythms; often, early premature impulses (i.e., during phase 3) resulted in either a shortened first return cycle or a short period of arrest of the rhythm. The results of this study indicate that it may be possible to design simple electrophysiologic tests using single premature stimuli to determine whether an arrhythmia is being caused by an automatic focus or by triggered activity.
The relationship between proton nuclear magnetic resonance relaxation parameters and myocardial perfusion with acute coronary arterial occlusion and reperfusion.
Authors: Ratner A V , Okada R D , Newell J B , Pohost G M
Published: June 2011

Previous investigators have demonstrated that acute myocardial ischemia, whether followed by reperfusion or not, is associated with prolongation of the proton nuclear magnetic resonance (NMR) relaxation times T1 and T2. Heretofore, the relationship between the severity of ischemia and alterations of these relaxation times has not been assessed. In our studies, changes in T1 and T2 were compared with myocardial perfusion in dogs both before and during 30 and 60 min of coronary arterial occlusion. In addition, studies were performed to assess the impact of reperfusion on relaxation times after 30 and 60 min of coronary occlusion. In the reperfusion studies the relationship between myocardial relaxation times and flow during the preocclusion, occlusion, and the 15 min reperfusion periods were studied. In the occlusion-only preparations, there was a significant inverse relationship between the relaxation times and flow during occlusion. In the reperfusion preparations there was a significant direct relationship between T1 and T2 and flow during the period of reperfusion. There was no significant relationship between the relaxation times and flow during occlusion in groups that subsequently underwent reperfusion, and no relationship between T1 and T2 and preocclusion flow in either the occlusion-only or reperfusion groups. These data suggest that the proton relaxation times provide an indication of the severity of an ischemic insult. Since NMR images can be generated that are sensitive to differences in these relaxation parameters, NMR imaging may provide a means to assess noninvasively the severity of the myocardial ischemic insult.
The relative merits of pulsus paradoxus and right ventricular diastolic collapse in the early detection of cardiac tamponade: an experimental echocardiographic study.
Authors: Klopfenstein H S , Schuchard G H , Wann L S , Palmer T E , Hartz A J , Gross C M , Singh S , Brooks H L
Published: June 2011

An inspiratory decline in systolic arterial blood pressure exceeding 10 mm Hg has been used clinically to identify hemodynamically significant pericardial effusions. Recently, the echocardiographic sign of right ventricular diastolic collapse (RVDC) has been shown to occur early in the course of cardiac tamponade in association with a hemodynamically important decline in cardiac output. This study was undertaken to compare the relative merits of pulsus paradoxus and the onset of RVDC in the early detection of cardiac tamponade in an unanesthetized canine preparation. We studied six chronically instrumented, conscious dogs with two-dimensional echocardiography during cardiac tamponade induced by continuous infusion of saline into the pericardial space. We recorded intrapericardial pressure, cardiac output (electromagnetic flowmeter), aortic (catheter-tip transducer) and right atrial blood pressures, heart rate, and respiration. None of the dogs had RVDC when the pericardial space was empty, but all dogs showed RVDC during cardiac tamponade. We found that RVDC was strongly related to all of the cardiac parameters evaluated (intrapericardial pressure, cardiac output, aortic blood pressure, heart rate, and stroke volume) and provided information on each that was independent of that provided by pulsus paradoxus. Furthermore, RVDC appeared to be more strongly related to most cardiac parameters than was pulsus paradoxus and to be more sensitive and specific than pulsus paradoxus in detecting changes in intrapericardial pressure early in cardiac tamponade.