bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of regional myocardial and renal blood flow with copper-PTSM and positron emission tomography.
Authors: Shelton M E , Green M A , Mathias C J , Welch M J , Bergmann S R
Published: June 2011

We recently demonstrated in isolated, perfused hearts that radiolabeled pyruvaldehyde bis(N4-methylthiosemicarbazonato)copper(II) (Cu-PTSM) is well extracted throughout a range of conditions including ischemia, hypoxia, and hyperemia. Once extracted, binding of radioactivity by the isolated heart was essentially irreversible, giving this tracer microspherelike qualities. Because Cu-PTSM can be readily prepared with the generator-produced positron-emitting copper 62 and other gamma- or positron-emitting copper radionuclides, we evaluated its usefulness for measuring regional myocardial and renal blood flow in vivo in intact dogs at rest, after ischemia, or after coronary hyperemia was induced by intravenous administration of dipyridamole. After intravenous administration of radiolabeled Cu-PTSM, the tracer cleared rapidly from the blood. Myocardial uptake of single photon-emitting 67Cu-labeled Cu-PTSM was measured directly in myocardial samples 15 minutes after tracer administration, and it increased proportionally with blood flow throughout the flow range (estimated concomitantly with radiolabeled microspheres) of 0.0-6.0 ml/g/min (n = 340 samples from 17 dogs, r = 0.99, Ycopper radioactivity = 85Xmicrosphere flow -7 chi 2 + 17). Renal uptake of radiolabeled Cu-PTSM was also proportional to blood flow. Positron emission tomography was performed in four intact dogs after intravenous administration of 64Cu-labeled Cu-PTSM (19% positron decay, t1/2 = 12.8 hours). High-quality images of heart and kidney were obtained. Accordingly, radiolabeled Cu-PTSM should be a useful, generator-produced tracer for estimating regional myocardial and renal blood flow with positron emission tomography.
Rate-modulated pacing.
Authors: Furman S
Published: June 2011

The primary role of cardiac rate in adapting cardiac output to changing physiological needs has been more clearly recognized in recent years. Previously, the rate of cardiac stimulation had been determined either at pacemaker manufacture, by programming a single rate, or by sensing the atrium. More recently, sensing another physiological or nonphysiological function that changes in response to body need has become possible. Exercise changes blood oxygen saturation, central venous pH, central venous temperature, minute ventilation and respiratory rate, stroke volume, circulating catecholamines, QT interval, evoked endocardial response to a stimulus, and the mechanics of myocardial contraction. Some sensors respond to muscle work but not to intellectual effort or emotion. Pacemaker-based sensors of physiological function or activity allow a change in cardiac stimulation rate in response to need. Whichever sensor is used, increases in ventricular rate during exercise regularly produce a cardiac output response. Single-chamber, rate-modulated pacemakers in atrium or ventricle and dual-chamber devices are now implanted on a widespread basis. These drive the atrium, the ventricle, or both, sensing or pacing the atrium at a rate determined by the sensor.
Eligibility for intravenous thrombolysis in suspected acute myocardial infarction.
Authors: Karlson B W , Herlitz J , Edvardsson N , Emanuelsson H , Sjölin M , Hjalmarson A
Published: June 2011

Based on the registration of all the 7,157 patients admitted during a 21-month period to the emergency ward of a single hospital in an urban area with chest pain or other symptoms suggestive of acute myocardial infarction, we studied eligibility for intravenous thrombolysis in suspected acute myocardial infarction. We have limited the present analysis to those 1,715 patients with a strong suspicion of myocardial infarction, and for these patients, we have calculated the percentages eligible for thrombolysis when various electrocardiographic and delay time criteria are applied, but we have not considered contraindications to thrombolysis. We have also calculated the proportions of all infarctions in this group that would thereby receive the treatment, and the proportions of patients treated that would develop a confirmed infarction. Using the criteria ST elevation on the initial electrocardiogram and arrival in hospital within 6 hours from onset of symptoms, 18% of patients would have been given early intravenous thrombolysis, 37% of confirmed infarctions would have been treated, and 91% of all treated patients would have developed a confirmed infarction; with a delay time criterion of 12 hours, these percentages would have been 20%, 41%, and 91%, respectively; with a criterion of 24 hours, they would have been 22%, 45%, and 90%, respectively. By not considering the initial electrocardiogram and applying only the criterion of delay time, these percentages would have been 70%, 72%, and 45%, respectively, for a delay time of 6 hours; 83%, 84%, and 45%, respectively, for a delay time of 12 hours; and 91%, 92%, and 44%, respectively, for a delay time of 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)
A quantitative evaluation of refractoriness within a reentrant circuit during ventricular tachycardia. Relation to termination.
Authors: Gottlieb C D , Rosenthal M E , Stamato N J , Frame L H , Lesh M D , Miller J M , Josephson M E
Published: June 2011

Programmed ventricular stimuli introduced during sustained monomorphic ventricular tachycardia frequently reset the tachycardia, resulting in a less than fully compensatory pause. A resetting response curve is generated when the set of return cycles is evaluated as the function of the coupling intervals of the extrastimuli delivered during the ventricular tachycardia. If the stimulated wave front encounters tissue within the tachycardia circuit that is not fully recovered, interval-dependent conduction changes should occur producing an increasing resetting response pattern. We quantified the magnitude of this interval-dependent conduction slowing in 17 morphologically distinct ventricular tachycardias. The slope of the increasing limb of the resetting response curve was determined by linear regression analysis and ranged from -0.30 to -1.14 (mean +/- SD, 0.70 +/- 0.25). Seven of the 17 ventricular tachycardias (41%) terminated during introduction of ventricular extrastimuli. The slope of the resetting response pattern in those ventricular tachycardias that terminated were significantly steeper than in those that did not terminate (-0.85 +/- 0.15 versus -0.61 +/- 0.21, respectively, p = 0.025). Six of the seven ventricular tachycardias terminated with programmed ventricular stimuli had a slope steeper than -0.75, whereas only one of 10 ventricular tachycardias that did not terminate exceeded this value. In conclusion, the slope of the increasing portion of the resetting response curve correlates with ability to terminate uniform sustained ventricular tachycardia by timed extrastimuli. This slope is the quantification of the magnitude of interval-dependent conduction slowing. Additionally, tissue within the reentrant circuit displaying greater degrees of interval-dependent conduction slowing may also have relatively longer effective refractory periods.
Fetal cardiac morphology of tetralogy of Fallot with absent pulmonary valve in the rat.
Authors: Momma K , Ando M , Takao A
Published: June 2011

Fetal in situ cardiovascular and bronchial morphologies were studied in rats with tetralogy of Fallot and absent pulmonary valve to clarify the prenatal pathology of this complex. There were 42 fetal rats with this complex among 300 fetuses treated with N,N'-bis-(dichloroacetyl)-1,8-octamethylenediamine (bis-diamine) (200 mg) on the 10th day of pregnancy. After undergoing rapid whole-body freezing on the 21st day, they were studied by means of serial cross-sectional photographs of the frozen thorax. Fetuses with normal heart treated with bis-diamine served as control. Tetralogy of Fallot and absent pulmonary valve in the fetus was associated with absence of the ductus arteriosus, enlargement and hypertrophy of both ventricles, and enlargement of the pulmonary arteries that compressed the bronchial trees. These abnormalities were inversely correlated with the degree of pulmonary stenosis. Milder stenosis (pulmonary valve ring greater than 50% of control, n = 28) was associated with larger pulmonary arteries (250 +/- 12% of control) (mean +/- SEM) and larger ventricles (volume, 200 +/- 15%; mass, 130 +/- 4%). Severe stenosis (pulmonary valve ring less than 50% of control, n = 14) was associated with mildly enlarged pulmonary arteries and mild bronchial compression. We concluded that enlargement of the pulmonary arteries and bronchial compression develop in fetal life and are associated with mild pulmonary stenosis in tetralogy of Fallot and absent pulmonary valve.
Cardiac tamponade in left ventricular dysfunction.
Authors: Hoit B D , Gabel M , Fowler N O
Published: June 2011

Echocardiographic and hemodynamic data were measured in closed-chest dogs during graded cardiac tamponade (pericardial pressure 5, 10, and 15 mm Hg) before and after production of diffuse ischemic left ventricular dysfunction. Left ventricular dysfunction was produced by intracoronary injection of nonradioactive microspheres (54 +/- 3.9 mm diameter). Changes in left atrial pressure with cardiac tamponade were influenced by coexisting left ventricular dysfunction. Left atrial pressure increased with tamponade and was equal to pericardial pressure before left ventricular dysfunction was produced. However, after left ventricular dysfunction was produced, left atrial pressure was significantly higher than pericardial pressure before tamponade, but it fell toward pericardial pressure when tamponade was produced. Pulsus paradoxus (greater than 10 mm Hg) was present in all animals with cardiac tamponade before left ventricular dysfunction but in only one animal afterward. During each level of tamponade, the inspiratory fall of aortic systolic pressure was greater before than with left ventricular dysfunction. The slope of the linear regression between pericardial pressure and millimeters of mercury of inspiratory fall in aortic systolic pressure was significantly greater before than with left ventricular dysfunction (0.74 +/- 0.12 versus 0.32 +/- 0.12, p less than 0.05). Left ventricular dysfunction caused a leftward and upward shift of the pericardial pressure-volume relation. As a result, right atrial and ventricular collapse occurred with significantly smaller volumes of pericardial fluid after than before left ventricular dysfunction. We conclude that pulsus paradoxus may be absent in cardiac tamponade with coexisting left ventricular dysfunction and unequal filling pressures. Echocardiographic signs of cardiac tamponade may occur with small effusions in the presence of left ventricular dysfunction.
Induction of plasminogen activator inhibitor by products released from platelets.
Authors: Fujii S , Sobel B E
Published: June 2011

Activation of platelets and augmentation of plasma plasminogen activator inhibitor (PAI) type I activity accompany acute myocardial infarction. To determine whether the two may be related, platelet compounds including epidermal growth factor and transforming growth factor beta as well as platelet lysates were studied in rabbits in vivo. After intravenous infusion of epidermal growth factor (1 and 5 micrograms/kg), plasma PAI activity increased sevenfold and 20-fold, peaking at 2 hours. After infusions of transforming growth factor beta (0.2 and 0.5 microgram/kg), plasma PAI activity increased sevenfold and 12-fold but peaked more slowly (at 5 hours). After infusion of platelet lysates (lysates from 2.8 and 5.6 X 10(8) platelets/kg), the increase was 19-fold and 35-fold, with a peak at 4 hours. Platelet lysates induced a pronounced increase of plasma PAI type 1 messenger RNA (Northern blots) in aorta, liver, and myocardium. Anti-transforming growth factor beta neutralizing antibody markedly attenuated the plasma PAI increase. Concentrations in plasma of fibrinogen and alpha 2-antiplasmin were virtually unaffected under all conditions. Thus, platelet-associated growth factors and platelet lysates, shown previously to increase plasma PAI type 1 messenger RNA expression and protein production in cultured hepatocytes and vascular endothelial cells in vitro, augment plasma PAI in vivo as well. Accordingly, activation of platelets and release of platelet-associated growth factors appear to contribute to the increased plasma PAI seen after myocardial infarction.
Baffle fenestration with subsequent transcatheter closure. Modification of the Fontan operation for patients at increased risk.
Authors: Bridges N D , Lock J E , Castaneda A R
Published: June 2011

Ventricular dysfunction, elevated pulmonary vascular resistance, and residual distal pulmonary artery distortion contribute to early mortality after a Fontan operation; they may be transient or reversible. A baffle fenestration, allowing right-to-left shunting, maintains cardiac output and limits right atrial pressure. A baffle fenestration was surgically created at the time of a modified Fontan repair in 20 consecutive patients. Risk factors included pulmonary artery pressure of 18 mm Hg or more, end-diastolic pressure of 12 mm Hg or more, valvar regurgitation, pulmonary artery distortion, pulmonary vascular resistance of 2 Woods' units or more, ventricular outflow obstruction, and complex anatomy. Nineteen of 20 patients survived. After the operation, mean arterial oxygen saturation was 86%, mean right atrial pressure was 15 mm Hg, and mean duration of pleural effusions was 6 days. Twelve of 19 survivors tolerated early test occlusion and had permanent transcatheter umbrella closure. Four patients failed early test occlusion, with a significant decrease in venous O2 saturation and a rise in central venous pressure, due to ventricular dysfunction, pulmonary artery distortion, or aortopulmonary collaterals. Three of four had successful late closure of the fenestration after correction of these abnormalities.
Iliofemoral arterial complications of balloon angioplasty for systemic obstructions in infants and children.
Authors: Burrows P E , Benson L N , Williams W G , Trusler G A , Coles J , Smallhorn J F , Freedom R M
Published: June 2011

The medical and radiological records of 64 consecutive infants and children who underwent transfemoral balloon dilation of the aorta or aortic valve were reviewed to determine the incidence, nature, and post-treatment outcome of acute iliofemoral complications. Balloon dilation angioplasty or balloon valvotomy was performed with 8F and 9F catheters without an arterial sheath. Patients ranged in age from 5 days to 15.4 years (mean, 6.4 years). Of 64 patients, 29 (45.3%) had an acute iliofemoral complication, including thrombosis (18 of 64), complete disruption (five of 64), incomplete disruption (three of 64), and arterial tear (three of 64). The arterial pathology was confirmed in 23 of 29 patients by one or a combination of surgical exploration and repair (18 of 29), angiography (six of 29), and magnetic resonance imaging (three of 29). Of eight patients, three with arterial disruption had acute hypotension requiring transfusion and immediate surgery; the other five had absent pedal pulses after the procedure. Of these five, three developed bleeding during thrombolytic therapy and underwent surgical exploration, and two were diagnosed by angiography after ineffective thrombolytic therapy. Angiography in three patients with iliac artery avulsion showed tapered occlusion in two and an aneurysm in one. In patients with iliofemoral thrombosis, angiography showed occlusion from the puncture site to the origin of the external iliac artery. Eleven patients (17% of the entire group and 38% of the group with acute iliofemoral complications) had reduced or absent pedal pulses at the time of discharge. A significant correlation was found between increased incidence of iliofemoral thrombosis and disruption (as well as abnormal pedal pulses at hospital discharge) and low patient weight.
Are the kinetics of technetium-99m methoxyisobutyl isonitrile affected by cell metabolism and viability?
Authors: Beanlands R S , Dawood F , Wen W H , McLaughlin P R , Butany J , D'Amati G , Liu P P
Published: June 2011

To investigate the role of cell viability and metabolism on the myocardial kinetics of a new tracer, technetium-99m-methoxyisobutyl isonitrile (Tc-99m-MIBI), 250 microCi/l Tc-99m-MIBI was infused in isolated rat hearts under constant flow conditions. The hearts were studied after inducing irreversible damage by cytochrome c oxidase inhibitor sodium cyanide (n = 8) or sarcolemmal membrane detergent Triton X-100 (n = 8). The control hearts (n = 6) received no toxins. Mean Tc-99m-MIBI peak accumulation activity was significantly reduced after cyanide (51.1 +/- 44.2% of control, p less than 0.01) and Triton (13.8 +/- 2.7% of control, p less than 0.001) administration. Kinetic studies also showed marked reduction in accumulation rates and marked increase in clearance rates for cyanide (p less than 0.01) and Triton (p less than 0.01) groups compared with controls. Potential changes in regional flow distribution were assessed using microspheres. When peak accumulation activity was corrected for these changes, there remained significant differences between the groups. In the cyanide and Triton groups, irreversible cell injury was confirmed by creatine kinase and lactate dehydrogenase release, triphenyl tetrazolium chloride staining, and electron microscopy. All the cells were viable in the control group. We conclude that the accumulation and clearance kinetics of Tc-99m-MIBI are significantly affected by cell viability. Tc-99m-MIBI kinetics appear to be dependent on sarcolemmal integrity and to a lesser extent on aerobic metabolism.
Uptake and retention of hexakis (2-methoxyisobutyl isonitrile) technetium(I) in cultured chick myocardial cells. Mitochondrial and plasma membrane potential dependence.
Authors: Piwnica-Worms D , Kronauge J F , Chiu M L
Published: June 2011

The fundamental myocellular uptake and retention mechanisms of hexakis (2-methoxyisobutyl isonitrile) technetium(I) (Tc-MIBI), a technetium-99m-based myocardial perfusion imaging agent, are unresolved. Because of the lipophilic cationic nature of Tc-MIBI, it may be distributed across biological membranes in response to transmembrane potential. To test this hypothesis, net uptake and retention of Tc-MIBI in cultured chick embryo ventricular myocytes were determined under conditions known to alter mitochondrial and plasma membrane potentials. Isovolumic depolarization of plasma membrane potentials in 130 mM extracellular K (Ko) 20 mM extracellular Cl buffer reduced net accumulation of Tc-MIBI from 171 +/- 16 (control) to 29 +/- 3.3 fmol intracellular Tc-MIBI/mg protein.nM extracellular Tc-MIBI. Unidirectional influx of Tc-MIBI in cells depolarized in 30 mM Ko buffer was also reduced; a resting plasma membrane potential of -87 +/- 6 mV was calculated from the Goldman flux equation using normal Ko/high Ko Tc-MIBI influx ratios. Addition of the potassium ionophore valinomycin to cells incubated in 130 mM Ko buffer to additionally depolarize mitochondrial membrane potentials further reduced net uptake of Tc-MIBI to levels comparable to that found in nonviable freeze-thawed preparations ([Tc-MIBI]i/[Tc-MIBI]o = 1). By depolarizing mitochondrial (and in part plasma membrane) potentials with the protonophores 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone (CCCP) Tc-MIBI was rapidly depleted from 181 +/- 16 (control) to 16 +/- 2.6 and 31 +/- 4.2 fmol/mg protein.nMo, respectively, with kinetics that did not correlate with loss of cellular ATP content. CCCP alone inhibited 90 +/- 3% of net accumulation or 66 +/- 3% of unidirectional influx of Tc-MIBI in a concentration-dependent manner. By hyperpolarizing mitochondrial membrane potentials with the K+/H+ ionophore nigericin or the ATP synthase inhibitor oligomycin, net uptake and retention of Tc-MIBI were increased by 60 +/- 9% and 375 +/- 20%, respectively. Caffeine, as well as the respiratory chain electron transport inhibitor rotenone, did not significantly alter net cell uptake (p greater than 0.2). These data indicate that the fundamental myocellular uptake mechanism of Tc-MIBI involves passive distribution across plasma and mitochondrial membranes and that at equilibrium Tc-MIBI is sequestered within mitochondria by the large negative transmembrane potentials.
Sotalol versus quinidine for the maintenance of sinus rhythm after direct current conversion of atrial fibrillation.
Authors: Juul-Möller S , Edvardsson N , Rehnqvist-Ahlberg N
Published: June 2011

This open, parallel-group study compares quinidine and sotalol treatment for maintenance of sinus rhythm after direct current conversion of patients with chronic atrial fibrillation. The patients from 15 centers in Sweden were randomized to sotalol (98 patients) or quinidine (85 patients) after 2 hours of sinus rhythm after direct current conversion. According to primary efficacy assessment, 52% of the patients in the sotalol group and 48% of the patients in the quinidine group remained in sinus rhythm during the following 6-month treatment period (NS). Furthermore, 34% of the patients treated with sotalol and 22% of the patients treated with quinidine relapsed into atrial fibrillation (NS). Heart rate after relapsing into atrial fibrillation was higher in the patients treated with quinidine (109 beats/min) than in the patients treated with sotalol (78 beats/min, p less than 0.001). Patients treated with sotalol were found to be less symptomatic at the time of relapse compared with relapsing patients in the quinidine group. In terms of safety, more patients were withdrawn from quinidine than from sotalol treatment (26% vs. 11%, p less than 0.05), and sotalol was generally better tolerated than quinidine. Twenty-eight percent of the patients treated with sotalol and 50% of the patients treated with quinidine reported side effects (p less than 0.01). The difference was primarily a result of early (within the first month of treatment) gastrointestinal and skin side effects in the group of patients treated with quinidine.(ABSTRACT TRUNCATED AT 250 WORDS)
A prospective, randomized, double-blind, crossover study to compare the efficacy and safety of chronic nifedipine therapy with that of isosorbide dinitrate and their combination in the treatment of chronic congestive heart failure.
Authors: Elkayam U , Amin J , Mehra A , Vasquez J , Weber L , Rahimtoola S H
Published: June 2011

We performed a prospective, randomized, double-blind, crossover study to compare the efficacy and safety of vasodilation with the calcium entry blocker nifedipine with that of isosorbide dinitrate (ISDN) and their combination as treatment for heart failure. Twenty-eight patients with New York Heart Association Functional class II or III chronic heart failure due to left ventricular systolic dysfunction were studied. All patients were maintained on a constant dose of digitalis and diuretics throughout the study. Eight weeks of therapy with nifedipine alone or in combination with ISDN resulted in a significantly higher incidence of heart failure deterioration necessitating hospitalizations and/or additional diuretics. Twenty-four percent of patients required hospitalization during nifedipine therapy and 26% required hospitalization during nifedipine-ISDN combination therapy in comparison to 0% requiring hospitalization during ISDN therapy alone. The total number of heart failure-worsening episodes was nine among patients on nifedipine, three among patients on ISDN (p less than 0.09 versus nifedipine), and 21 among patients on nifedipine-ISDN combination (p less than 0.001 versus nifedipine, p less than 0.0001 versus ISDN). Premature discontinuation of drug administration due to clinical deterioration or other side effects occurred in 29% of patients during nifedipine therapy, 5% of patients during ISDN therapy (p = 0.05 versus nifedipine), and 19% of patients during the combination therapy. A comparison of eight patients who demonstrated clinical deterioration on nifedipine with the remainder of the patients demonstrated no significant difference in left ventricular ejection fraction (0.24 +/- 0.06 versus 0.23 +/- 0.07) or maximal oxygen uptake during exercise (13 +/- 3 versus 14 +/- 2 ml/kg/min).(ABSTRACT TRUNCATED AT 250 WORDS)
Differentiation of ventricular tachyarrhythmias.
Authors: Ropella K M , Baerman J M , Sahakian A V , Swiryn S
Published: June 2011

Implantable devices capable of several modes of therapy will require differentiation of various ventricular tachyarrhythmias. Three methods of arrhythmia analysis, magnitude-squared coherence, ventricular rate, and irregularity of cycle length were performed for 45 episodes of induced ventricular tachyarrhythmia in 15 patients. Differentiation of monomorphic ventricular tachycardia from polymorphic ventricular tachycardia and ventricular fibrillation was possible by mean magnitude-squared coherence, less possible by rate, and not possible by beat-to-beat irregularity. Faster monomorphic ventricular tachycardia overlapped with rates of polymorphic ventricular tachycardia and ventricular fibrillation. Differentiation of polymorphic ventricular tachycardia and ventricular fibrillation was not possible by rate or irregularity. A progressive decrease in mean magnitude-squared coherence from monomorphic ventricular tachycardia to polymorphic ventricular tachycardia to ventricular fibrillation strengthens previous observations that coherence is a measure of rhythm "organization."
Sympathetic nervous system-dependent vasoconstriction in humans. Evidence for mechanistic role of endogenous purine compounds.
Authors: Taddei S , Pedrinelli R , Salvetti A
Published: June 2011

Purine compounds modulate sympathetic neurotransmission; this modulation decreases nervous discharge by stimulating presynaptic inhibitory adenosine receptors, an effect antagonized by theophylline, and causes vasoconstriction through the stimulation of postsynaptic ATP receptors. In humans we evaluated the effect of local theophylline, which was infused into the brachial artery at the rate of 100 micrograms/100 cc/min, on the arteriolar sympathetic vasoconstriction induced by applying a lower-body negative pressure. Forearm blood flow changes were measured by strain-gauge venous plethysmography. Theophylline, which at this dosage blunted the vasodilator effect of adenosine (the physiological agonist for the P1 purinoceptor), significantly increased lower-body negative pressure-mediated vasoconstriction. To evaluate whether neurotransmitters different from norepinephrine participate in the vasoconstrictor effect of theophylline, we repeated the previous experiment in the presence of phenoxybenzamine, which was infused at a dose (60 micrograms/100 cc/min) that abolished the vasoconstrictor effect of norepinephrine. Also, after alpha-adrenoceptor blockade, theophylline continued to increase sympathetic vasoconstriction. Our data confirm that purinergic receptors and neurotransmitters also participate in endogenous sympathetic vasoconstriction in humans.
Body surface mapping of high-frequency components in the terminal portion during QRS complex for the prediction of ventricular tachycardia in patients with previous myocardial infarction.
Authors: Shibata T , Kubota I , Ikeda K , Tsuiki K , Yasui S
Published: June 2011

To study the clinical significance of terminal QRS high-frequency components for the prediction of ventricular tachycardia, an 87-lead body surface signal-averaged mapping was performed in 21 healthy subjects (control) and in 41 patients with previous myocardial infarction (anterior, 20; inferior, 21). Mapping data were analyzed and averaged (129.7 +/- 26.5 beats) for 160 seconds, and the signal-averaged beat was filtered with a bidirectional bandwidth (80-250 Hz) digital filter. J-point was determined from the 87-lead RMS voltage of nonfiltered QRS. For each lead, we calculated the sum of the absolute value of filtered QRS from 20 msec ahead of the J-point to the J-point (A-20). The body surface distribution of A-20 was expressed as A-20 map. The maxima in A-20 maps were mainly located on the upper sternal region in healthy subjects, on the left anterior chest in patients with previous anterior myocardial infarction, and on the central anterior chest in patients with previous inferior myocardial infarction. In the patients in both the group with anterior myocardial infarction and the group with inferior myocardial infarction, the value of maximum was significantly greater than in the subjects in the control group (0.181 +/- 0.086 and 0.138 +/- 0.048, respectively, vs. 0.075 +/- 0.031 mV.msec; p less than 0.01). In patients with myocardial infarction (n = 41), the value of maximum was significantly greater with ventricular tachycardia (n = 11) than without ventricular tachycardia (n = 30) (0.240 +/- 0.076 vs. 0.130 +/- 0.043 mV.msec; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Significance of discordant ST alternans in ventricular fibrillation.
Authors: Konta T , Ikeda K , Yamaki M , Nakamura K , Honma K , Kubota I , Yasui S
Published: June 2011

With the use of epicardial mapping, we investigated the electrical alternans of the ST segment during acute myocardial ischemia and studied the difference in ST alternans between dogs with resultant ventricular fibrillation and those without it. During the 7-minute occlusion of the left anterior descending coronary artery below its first diagonal branch, 60 epicardial unipolar electrograms were recorded simultaneously at 1-minute intervals by a computerized mapping system. ST alternans was found in the eight dogs we observed. The amplitude of ST alternans (difference in the ST segment elevation of two consecutive electrograms) was greater in dogs with ventricular fibrillation (n = 4) than in those without it (n = 4) (3.92 +/- 1.24 versus 0.58 +/- 0.49 mV, p less than 0.05). Three of the four dogs with ventricular fibrillation demonstrated discordant ST alternans (i.e., adjacent leads were out of phase). Results from the present study indicate that an increased amplitude and discordance of ST alternans during acute myocardial ischemia are related to ventricular fibrillation and act as indicators of time and spatial unevenness of ventricular repolarization.
Assessment of Cerebral Circulation (Cortical Blood Flow) with an Infrared Microscope
Authors: ANDERSON ROBERT E. , WALTZ ARTHUR G. , M.D. TAKENORI YAMAGUCHI , OSTROM ROBERT D.
Published: June 2011

An infrared microscope was used for the remote detection of the surface temperature of the cerebral cortex of experimental cats. With this instrument a qualitative assessment of the circulation of the cerebral cortex can be made without interference with the integrity of the brain or vascular tissues or the reactivity of blood vessels. Although the instrument is sensitive enough to detect minor changes of cortical blood flow, its use appears limited to the detection of rapid or transient changes of cerebral circulation and is not suitable for long-term measurements of surface temperature of the brain.
The Smaller Intracerebral Vessels
Authors: ELLINGTON ANNA L.
Published: June 2011

A pathological study of the smaller intracerebral arteries of 150 to 600µ was made in 336 cases, ranging in age from 1 day to 96 years. The changes involved the media and adventitia in contradistinction to the large cerebral vessels which showed predominantly intimal changes. The degree of change in the smaller intracerebral arteries was age related but not on a 1:1 basis. A comparison of the degree of change was also made with the large cerebral vessels of the circle of Willis, and although both were age related, they did not appear to be related to each other.
Coagulation Abnormalities in Subarachnoid Hemorrhage
Authors: ETTINGER M. G.
Published: June 2011

Coagulation and fibrinolytic studies were performed in 30 subarachnoid hemorrhage patients and 30 age-matched and sex-matched controls.

Systemic abnormalities were detected in the following tests: recalcification time, fibrinogen, partial thromboplastin time, K value of thromboelastogram and euglobulin lysis time.

The data suggest that subarachnoid hemorrhage patients with fibrinogen values over 400 mg% have a low probability of survival.

Test abnormalities probably reflect tissue damage and/or meningeal reaction to the subarachnoid hemorrhage. Similar abnormalities can be noted in patients with cerebral trauma and in some patients with nonhemorrhagic cerebrovascular disease.
1

Our data reveal that subarachnoid hemorrhage patients may exhibit simultaneously evidence suggesting increased coagulability and activation of fibrinolytic mechanisms. Under these circumstances administration of agents to suppress lytic activity might lead to disastrous consequences such as widespread intervascular coagulation (consumption coagulopathy).
Cardiac Disorders Predisposing to Embolic Stroke
Authors: KANE WALTER C. , ARONSON STANLEY M.
Published: June 2011

Data from 4,558 consecutive complete necropsies in patients 16 years of age or older were analyzed to ascertain the influence of certain variables upon the frequency of embolic encephalomalacia.

Embolic lesions of the central nervous system occurred more commonly in the female, regardless of age, race, diabetic status, nutritional status or heart size, partly because the cardiovascular lesions responsible for embolic dissemination were more common in women. While affecting only a small percentage of patients at any age, cerebral embolism assumes more importance in strokes of young adulthood. Embolic infarcts demonstrate a predilection for cerebral and cerebellar cortical locations via the long circumferential arterial branches and tend to spare the parasagittal perforating branches supplying the brain stem and diencephalic nuclei.

Certain cardiac states predispose to cerebral embolism. Patients with endocarditis show the greatest risk of embolic lesions, although patients with rheumatic valvular disease of the left heart and mural thrombi of the left ventricle produce numerically more cases of embolic encephalomalacia because these conditions occur far more often than the endocardidites.
Experimental Cerebral Infarction. I. Selective Segmental Occlusion of Intracranial Arteries in the Dog
Authors: MOLINARI GAETANO F.
Published: June 2011

1. Cylinders of silicone rubber can be molded to any desired diameter and cut to length, yielding a highly pigmented, radio-opaque, elastic bolus suitable for intravascular injection and embolization.

2. Emboli of this type can be localized by x-ray in vivo and at post mortem for clinicopathological correlation studies.

3. Segments of specific vessels of known diameter can be selectively occluded with a high degree of predictability.

4. The caliber of the proximal segment of the middle cerebral artery is remarkably constant in dogs. The extracranial arteries, however, vary proportionately to the body weight of the animal.

5. Proximal segmental occlusion of the middle cerebral artery results in occlusion of the origins of the lenticulostriate vessels. This produces a deep ischemic infarction of basal ganglia and internal capsule. The cerebral cortex is spared due to the integrity of meningocerebral anastomotic network.
Blood Flow in the Central and Peripheral Nervous System of Dogs Using a Particle Distribution Method
Authors: TSCHETTER THOMAS H. , KLASSEN ARTHUR C. , RESCH JOSEPH A. , MEYER MAURICE W.
Published: June 2011

In this study known activities of
85
Sr and
169
Yb-labeled microspheres were injected sequentially into the left ventricle of anesthetized dogs. Cardiac output was determined before and after each microsphere injection. Blood flow to brain, brain stem, spinal cord, and sciatic nerve was measured from fractional distribution of the microspheres in the tissue samples. Both blood flow and fractional uptake value tended to be higher for brain and brain stem than for spinal cord or sciatic nerve. Increases in arterial Pa

CO
CO2

were positively correlated with increases in blood flow to both central and peripheral nervous tissue. Initial trapping of the labeled microspheres seems to have little effect on subsequent flow to the tissue capillary bed. It appears that the particle distribution technique may provide a reasonable estimate of blood flow in central and peripheral nervous tissue of dogs.
Improved results of carotid endarterectomy in patients with symptomatic coronary disease: an analysis of 1,546 consecutive carotid operations.
Authors: Ennix C L , Lawrie G M , Morris G C , Crawford E S , Howell J F , Reardon M J , Weatherford S C
Published: June 2011

The significant risk of fatal myocardial infarction after carotid endarterectomy in patients with coronary disease long has been recognized. In 1,546 consecutive carotid endarterectomies performed in 1,238 patients over the last 10 years, angina pectoris was present in 17% (212/1,238) of patients; a further 32% (396/1,238) of patients were asymptomatic, but had a history of myocardial infarction. The perioperative mortality (30 day) in the 1,306 consecutive endarterectomies in 1,026 patients without symptomatic coronary artery disease was 1.5% (15/1,026 patients). Of the 212 patients with symptoms, 85 carotid endarterectomies were performed in 77 patients without prior coronary bypass operation with an operative mortality of 18.2% (14/77 patients). The remaining 135 patients had 155 carotid endarterectomies but were treated by either prior coronary artery bypass (84 patients) or simultaneous carotid endarterectomy and coronary artery bypass (51 patients) with an operative mortality of 3% (4/135 patients). The greatly improved survival in those patients with symptomatic coronary disease who had a coronary artery bypass prior to or at the same time as carotid endarterectomy, and the absence of permanent neurological deficit in the 51 of these 135 patients who had simultaneous carotid endarterectomy and coronary artery bypass suggests that significantly improved survival can be achieved after carotid endarterectomy in these high risk patients by the use of simultaneous coronary artery bypass surgery.
Cervical carotid aneurysm presenting as recurrent cerebral ischemia with head turning.
Authors: Countee R W , Vijayanathan T , Barrese C
Published: June 2011

Extracranial carotid artery aneurysms are uncommon lesions with protean manifestations. This report describes a patient in whom the presenting symptom of a right carotid aneurysm was recurrent right hemisphere ischemic attacks when he turned his head to the left. The angiographic and operative findings explained the mechanism(s) of his symptoms. The importance of such symptoms is that they should suggest a mechanical etiology and that the probability of a surgically correctable lesion exists. Arteriography is the only reliable means of making a definitive diagnosis and should be considered early in the evaluation.
Survival of rabbits after prolonged cerebral ischemia.
Authors: Kolata R J
Published: June 2011

Cerebral ischemia was produced by a combination of vascular occlusion and mild systemic hypotension in 2 groups of rabbits. Arterial blood pressure, arterial pH, arterial blood gases, blood glucose and PCV were monitored and recorded before, during and for 3 hours after reperfusion. Return of EEG activity, vasomotor control, spontaneous ventilation and corneal reflex were also recorded. At 4, 8, 12, 24 and 48 hours after reperfusion, the rabbits' neurologic status was assessed according to an arbitrary scale based on motor function. The 2 groups differed in return of reflexes and motor function. Eighty percent of the rabbits ischemic for 20 minutes and 75% of the rabbits ischemic for 30 minutes survived. The graduated response of motor function to cerebral ischemia is attributed to the ventilatory and circulatory support given the rabbits for the first 3 hours after reperfusion. The graduate response of motor function to ischemia supports the suggestion that motor function can be used as an index of neurologic damage.
Dissecting aneurysms of the basilar artery in 2 patients.
Authors: Alexander C B , Burger P C , Goree J A
Published: June 2011

An uncommon consequence of intracranial vascular disease is the intramural dissection of blood or "dissecting aneurysm". A 69-year-old man with chronic subarachnoid hemorrhage from a posterior fossa mass lesion and a 30-year-old man with migraine and a brain stem stroke illustrate the diverse etiologic, clinical, radiographic, and pathologic characteristics of this unusual lesion.
Flow disturbances at the apex and lateral angles of a variety of bifurcation models and their role in development and manifestations of arterial disease.
Authors: Malcolm A D , Roach M R
Published: June 2011

Dye flow patterns were studied in 12 glass model bifurcations with angles of 45, 90, 135, and 180 degrees, and area ratios of 0.78, 1.03 and 1.27. At the apex, the dye formed a saddle zone, and streamlines from the core which entered this region were swept over the upper and lower surfaces to enter the lateral angles. Qualitatively, the shape and size of the apex played a key role in this effect. Boundary layer separation occurred in the lateral angles, and increased as flow into the branch was reduced. If the branch was occluded, a complex vortex developed in the first few diameters of the branch, and no flow occurred beyond this, even though the occlusion was about 20 diameters downstream. The results were comparable with steady and pulsatile flow. The implications of these results for the localization of atherosclerosis are discussed.
Autopsy study of cerebrovascular disease in Japanese men who lived in Hiroshima, Japan, and Honolulu, Hawaii.
Authors: Mitsuyama Y , Thompson L R , Hayashi T , Lee K K , Keehn R J , Resch J A , Steer A
Published: June 2011

Evidence of cerebrovascular disease at autopsy was compared in 2 groups of men: 186 long-time residents of Hiroshima, Japan, and 253 men of Japanese ancestry long resident in Honolulu, Hawaii. They were 45 to 71 years-of-age at death. Atherosclerosis of the circle of Willis and its major branches, sclerosis of the intraparenchymal arteries and the frequency of cerebral hemorrhage and cerebral infarct were compared in the 2 populations. The Honolulu subjects had significantly more atherosclerosis of the circle of Willis, but less intraparenchymal artery sclerosis and less cerebral infarction. Cerebral hemorrhage was equally frequent in the 2 cities. It was concluded that cerebral infarction is more frequent in Japanese men in Hiroshima than Honolulu, and that men of Japanese ancestry in Honolulu are spared an appreciable risk of cerebral infarction through decreased frequency of intraparenchymal arterial sclerosis despite higher levels of atherosclerosis of large intracranial arteries.
A new canine model of proximal internal carotid embolism.
Authors: Kaufman H H , Anderson J H , Huchton J D , Woo J
Published: June 2011

A new model of internal carotid artery embolism was developed using autologous clot. The clot was prepared by incubating blood at room temperature for 2 hours to inactivate plasminogen activators and then refrigerating it at 4 degrees C for 22 hours. The purpose of the experiment was to devise a model of the intravascular lesion and not of stroke itself. The dog was chosen as the experimental animal since it has a maxillocarotid artery which permits collateral flow beyond proximal internal carotid artery occlusions. A volume of clot measuring 0.25 to 0.30 cc was sufficient to occlude the artery for 48 hours in 80% of the animals without causing major strokes. We have used this model to study clot radiolabeling and suggest it may also have application for evaluating thrombolytic drugs.
Treatment of acute focal ischemia with continuous CSF drainage and mannitol.
Authors: Little J R , O'Shaughnessy D
Published: June 2011

A simple implanted device was used to occlude acutely the left middle cerebral artery (MCA) of 32 conscious cats. Groups of 18 cats each were treated with continuous cerebrospinal fluid (CSF) drainage, mannitol (1 gm/kg i.v.), or a combination of continuous CSF drainage and mannitol (1 gm/kg i.v.). Eight cats served as a control group. The neurological status of cats treated with mannitol improved transiently. Perfusion with a mixture of colloidal carbon and buffered paraformaldehyde was carried out 12 hours following MCA occlusion. Gross swelling of cerebral tissue, distribution of colloidal carbon, and breakdown of the blood-brain barrier to fluorescein were similar in the 4 groups. Reduction of mean capillary luminal diameter to 4.5 +/- 1.0 micron (control 6.5 +/- 1.0 micron) in the left Sylvian cortex was unaltered by treatment. A significant difference in the distribution of severe neuronal alterations was not demonstrated.
Circulating platelet aggregates in sickle cell disease patients with and without vaso-occlusion.
Authors: Mehta P , Mehta J
Published: June 2011

In vivo circulating platelet aggregates (CPA) were evaluated in 18 patients aged 6 to 17 years with sickle cell disease and in 11 age and sex matched normal subjects. Twelve patients with sickle cell disease were in steady state and 6 had vaso-occlusive crises. CPA in patients in steady state were similar to those in normal subjects (mean 6 +/- 1% compared to 5 +/- 2%, respectively), whereas patients with vaso-occlusive crisis in acute state had significantly higher CPA (mean 39 +/- 8%) than patients in steady state or normal control individuals (both p less than 0.001). CPA decreased in patients with vaso-occlusive crisis (mean 11 +/- 4%) on the tenth day, in association with clinical improvement. This study suggests that in vivo platelet aggregate formation activity, although normal in sickle cell disease patients in steady state, is significantly increased in patients with vaso-occlusive crises.
Tranexamic acid in subarachnoid hemorrhage. A double-blind study.
Authors: Kaste M , Ramsay M
Published: June 2011

The effects of intravenous tranexamic acid were compared with placebo in 64 patients with subarachnoid hemorrhage. A double-blind procedure was used. One gram of tranexamic acid was given intravenously every 4 hours up to the time of operation on an intracranial arterial aneurysm or for up to 21 days after the first bleeding if operative treatment was not feasible. There were no differences in re-bleeds, morbidity or mortality between the tranexamic and placebo-treated groups. No thromboembolic complications were noted in either group. Our results do not support the use of tranexamic acid in subarachnoid hemorrhage in daily doses of 6 g.
Prognosis in patients with infarction and TIA in carotid territory during and after anticoagulant therapy.
Authors: Link H , Lebram G , Johansson I , Rådberg C
Published: June 2011

One hundred seventeen patients, 31 with TIA and 86 with cerebral infarction, had angiographically verified atherosclerosis within the relevant carotid artery territory and normal CSF. They were treated with anticoagulants for a mean of 11.1 months. No TIA but 1 cerebral infarction, appearing during inadequate anticoagulant therapy, was registered. Seventy-six of the patients, 20 with TIA and 56 with infarction, were followed for a mean of 4.4 months after cessation of anticoagulants or during inadequate antinecessitating re-institution of anticoagulant therapy. Long-term, anticoagulant treatment can be recommended in carefully selected patients with TIA, and also with infarction in the carotid territory.
Chronic subdural hematoma presenting as transient neurologic deficits.
Authors: Welsh J E , Tyson G W , Winn H R , Jane J A
Published: June 2011

Four patients with symptoms of transient neurological dysfunction were subsequently found to have chronic subdural hematomas (CSDH). The frequency of these episodes diminished significantly after evacuation of the hematoma. The effects of vascular compromise due to the CSDH and to cardiovascular events, more commonly implicated in transient ischemic attacks (TIAs) may be additive. The inclusion of a computerized axial tomographic (CAT) scan in the evaluation of some patients with presumed TIAs is recommended.