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Biomedical subjects

Y Birnbaum

Publications and source records attributed to Y Birnbaum.

At least 73 records · Page 4Linked to original sources
PubMed1998

A small animal model of non-ischemic cardiomyopathy and its evaluation by transthoracic echocardiography.

BACKGROUND: Costs for large animal studies have escalated. Therefore there is a need to develop small animal models of non-ischemic cardiac failure and accurate non-invasive techniques that will allow serial quantitation of left ventricular function. OBJECTIVES: The purpose of our study was to determine the efficacy and reliability of adriamycin for inducing cardiomyopathy in rats. We hypothesized that high frequency transthoracic 2-dimensional and M-mode echocardiography would allow for serial testing of cardiac function in this small animal model. METHODS: Adriamycin was administered at a dose of 2.5 mg/kg intravenously once a week for 10 weeks in 54 rats. Transthoracic echocardiography by use of a 7.5 MHz transducer was performed in 19 rats at baseline and additionally at 12 weeks after beginning of adriamycin therapy to measure left ventricular dimensions and calculate fractional shortening. RESULTS: The mortality rate during the treatment period was 11%, but increased to 52% at 13 weeks. Transthoracic echocardiography provided adequate visualization of left ventricular dimensions and cardiac function in a parasternal short axis view. In follow-up echocardiography, pericardial effusion was detected in 8/19 rats (42%). Compared to baseline, end-diastolic diameters increased from 0.56 +/- 0.06 to 0.64 +/- 0.08 mm (p < 0.001), end-systolic diameters increased from 0.27 +/- 0.03 to 0.42 +/- 0.08 mm (p < 0.001), and fractional shortening decreased from 52.8 +/- 4.0 to 34.3 +/- 7.1% (p < 0.001) at 12 weeks. Electron microscopy in a subset of rats revealed cardiomyocyte degeneration, mitochondrial and sarcoplasmatic reticular edema, numerous intracellular vacuoles and 'onion-ring' shaped mitochondrial cristae, characteristic for adriamycin cardiotoxicity in human patients. CONCLUSION: Adriamycin at an intravenous dose of 2.5 mg/kg over 10 weeks can be used to create a reliable model of non-ischemic dilated cardiomyopathy with a high success rate. For in-vivo diagnostic purposes, transthoracic echocardiography provides a reliable technique to non-invasively assess cardiac function quantitatively and qualitatively in follow-up studies in rat cardiomyopathy. This small animal model can easily be used for testing new therapeutic strategies in cardiac failure.

Animals↗
PubMed1998

Cooling System Permits Effective Transcutaneous Ultrasound Clot Lysis In Vivo Without Skin Damage.

Previous in vivo studies have shown that transcutaneous ultrasound enhances clot dissolution in the presence of either streptokinase or microbubbles. However, ultrasound-induced skin damage has been a major drawback. The objective was to evaluate the effect of a cooling system to prevent the skin damage that has heretofore been associated with transcutaneous low-frequency, high-intensity ultrasound clot dissolution. After thrombi were induced in both iliofemoral arteries in 15 rabbits, streptokinase (25,000 U/kg) was given intravenously and dodecafluoropentane was injected slowly (2 mL/15 min) through an infusion catheter into the abdominal aorta. One iliofemoral artery was randomized to receive ultrasound treatment, and the contralateral artery was treated as a control (receiving streptokinase and dodecafluoropentane alone). In six rabbits (group 1), the skin below the ultrasound transducer was protected by the use of a balloon cooling system, and in the other nine rabbits (group 2), ultrasound was used without a cooling system. Seven of nine (78%) arteries treated without the cooling system, and six of six (100%) arteries treated with the cooling system were angiographically recanalized after ultrasound + streptokinase + dodecafluoropentane treatment. Thermal damage was present in the skin and soft tissues of all nine rabbits treated without a cooling system. However, the skin and soft tissues were grossly and histologically normal in the six rabbits in which the transcutaneous ultrasound was used with the cooling system. Low-frequency, high-intensity ultrasound energy can be delivered transcutaneously for clot dissolution without concomitant tissue damage when coupled with the use of a cooling system to prevent thermal injury.

Journal Article↗
PubMed1998

QRS complex distortion predicts no reflow after emergency angioplasty in patients with anterior wall acute myocardial infarction.

BACKGROUND: In patients with acute myocardial infarction, distortion of the terminal portion of the QRS complex on the electrocardiogram (ECG) at the time of their admission to hospital is associated with larger final infarct size and greater mortality. This study assessed the results of emergency coronary angioplasty in patients with anterior acute myocardial infarction with and without distortion of the terminal portion of the QRS complex on the admission ECG. METHODS: We assessed the Thrombolysis in Myocardial Infarction (TIMI) trial flow grade, resolution of ischemic ECG changes, and clinical outcome after emergency angioplasty for acute anterior wall myocardial infarction in patients with (n = 21) and without (n = 21) distortion of the terminal portion of the QRS complex on the admission ECG. RESULTS: Compared with patients without distortion of the terminal portion of the QRS complex on the admission ECG, those with distortion had a significantly lower incidence of TIMI flow grade 3 (52% compared with 84%, P < 0.05), lower rate of resolution of the ischemic ECG changes (33% compared with 84%, P < 0.005), and greater rate of mortality during their stay in hospital despite successful balloon angioplasty (19% compared with 0%, P < 0.05). CONCLUSIONS: In patients with anterior wall acute myocardial infarction, distortion of the terminal portion of the QRS complex on the admission ECG predicts a greater mortality rate and a greater incidence of reflow impairment after emergency angioplasty.

Adult↗
PubMed1998

Early development of high-degree atrioventricular block in inferior acute myocardial infarction is predicted by a J-point/R-wave ratio above 0.5 on admission.

This study assessed the ability of simple clinical and electrocardiographic (ECG) variables routinely obtained on admission to identify patients with inferior myocardial infarction who are at high risk of developing high-degree atrioventricular (AV) block within the first 24 h of hospitalization in 205 patients. The admission ECGs were classified into two patterns based on the J-point to R-wave amplitude ratio: pattern 1: those with J-point/R-wave ratio <0.5; pattern 2: patients with J-point/R-wave ratio >/=0.5 in >/=2 inferior leads (II, III and aVF). High-degree AV block was found in 10.2% of the patients (21 of 205 patients; 5 and 16% of the patients with initial patterns 1 and 2, respectively, p = 0.014). Multivariate logistic regression analysis revealed that the only variables independently associated with high-degree AV block were the initial ECG pattern 2 versus 1 (odds ratio, OR, 4.47, 95% confidence interval, CI, 1.18-16.9; p = 0.0276), age (OR 1.06, 95% CI 1.01-1.12; p = 0.0254); Killip class >1 (OR 2.33, CI 0.83-6. 54; p = 0.1065) and thrombolytic therapy (OR 0.32, 95% CI 0.11-0.93; p = 0.037).

Adult↗
PubMed1998

Are there differences among patients with inferior acute myocardial infarction with ST depression in leads V2 and V3 and positive versus negative T waves in these leads on admission?

We assessed whether there are differences among patients with inferior acute myocardial infarction and ST segment depression in leads V2-V3 between those with positive versus negative T waves on admission. We found no differences in the prevalence of concomitant significant left anterior descending coronary artery stenosis and anterior or posterior wall motion abnormalities on echocardiography between the two groups. Precordial ST segment depression with negative T wave may be the early electrocardiographic pattern of posterior infarction, reflecting ST segment elevation with positive T waves that would have been detected by leads facing the posterior wall.

Cohort Studies↗
PubMed1997

Admission clinical and electrocardiographic characteristics predicting in-hospital development of high-degree atrioventricular block in inferior wall acute myocardial infarction.

This study assessed the ability of simple clinical and electrocardiographic variables routinely obtained on admission to identify patients who are at high risk of developing high-degree atrioventricular (AV) block during hospitalization in 1,336 patients with inferior wall acute myocardial infarction (AMI). Patients were classified into 2 initial electrocardiographic patterns based on the J-point to R-wave amplitude ratio: pattern 1: those with J point/R wave <0.5 and pattern 2: patients with J point/R wave > or =0.5 in > or =2 leads of the inferior leads II, III, and aVF. High-degree AV block was found in 6.7% of patients (41 of 615) with pattern 1 versus 11.8% of the patients (85 of 721) with pattern 2 on admission electrocardiogram (p = 0.0008). Multivariate logistic regression analysis revealed that the only variables found to be independently associated with high-degree AV block were female gender (odds ratio [OR] 1.48; 95% confidence interval [CI] 0.98 to 2.23; p = 0.06); Killip class on admission > or =2 (OR 2.24; CI 1.43 to 3.51; p = 0.0004); initial electrocardiographic pattern 2 versus pattern 1 (OR 1.82; CI 1.22 to 2.21; p = 0.003); and absence of abnormal Q waves on admission (OR yes vs no 0.68; CI 0.44 to 1.05; p = 0.08). A simple electrocardiographic sign (J point/R wave > or =0.5 in > or =2 leads) is a reliable predictor of the development of advanced AV block among patients receiving thrombolytic therapy for inferior wall AMI.

Case-Control Studies↗
PubMed1997

Regional remodeling of atherosclerotic arteries: a major determinant of clinical manifestations of disease.

In this review we present the current data on remodeling, based on in vivo ultrasound imaging or postmortem histologic analysis of native peripheral and coronary arteries from animal models and studies in patients (coronary artery saphenous vein bypass grafts, lesions of restenosis after balloon angioplasty and other catheter-based interventions). Histologic and ultrasound imaging studies of arteries with atherosclerosis and after vascular injury reveal that arterial remodeling is common and that the cross-sectional area of the vessel is not constant. Compensatory enlargement, inadequate compensatory enlargement and shrinkage at the site of atherosclerotic lesions occurs in coronary and peripheral arteries. Current studies demonstrate that arterial remodeling is a major determinant of vessel lumen size.

Angioplasty, Balloon, Coronary↗
PubMed1997

Ischemic preconditioning at a distance: reduction of myocardial infarct size by partial reduction of blood supply combined with rapid stimulation of the gastrocnemius muscle in the rabbit.

BACKGROUND: Limitation of myocardial infarct size by an earlier brief complete occlusion of a coronary artery is defined as ischemic preconditioning. However, myocardial protection also can be achieved by partial reduction of coronary flow, rapid cardiac pacing, or brief ischemia-reperfusion of a remote region of the heart. Our study assesses the effect on myocardial infarct size of preconditioning at a distance induced by partial reduction of blood flow to a hind limb with or without increase of demand by electrical stimulation of a skeletal muscle. METHODS AND RESULTS: Anesthetized rabbits were randomized to 30 minutes of waiting period (controls), 55% to 65% reduction of femoral artery blood flow (stenosis), electrical stimulation of the gastrocnemius muscle at a rate of one per second (stimulation), or stenosis+stimulation. Thereafter, rabbits underwent 30 minutes of coronary artery occlusion and 4 hours of reperfusion. Each group included 8 rabbits. Risk zones were comparable among groups. However, the ratio of infarct size to risk zone was smaller in the stenosis+stimulation group (0.09+/-0.02) compared with the control (0.26+/-0.03), stenosis (0.36+/-0.05), and stimulation (0.30+/-0.05) groups (P=.0006). ANCOVA performed on the fraction of infarction (infarct size/left ventricular weight) and the fraction of risk zone revealed a significant group effect (P=.0004). CONCLUSIONS: Remote ischemia of a skeletal muscle induced by muscle stimulation combined with restriction of blood flow preconditioned the myocardium. The combination of muscle stimulation with reduction of femoral arterial blood flow but not muscle stimulation without blood flow restriction or of flow restriction without muscle stimulation reduced myocardial infarct size considerably.

Animals↗
PubMed1997

Documentation by intravascular ultrasound of thrombus overlying a small atheromatous plaque in a coronary artery in unstable angina pectoris and in acute myocardial infarction.

Rupture of atheromatous plaques leading to acute coronary syndromes usually occur in lipid-reach and well-developed coronary lesions. We describe 2 unusual patients with acute coronary syndromes in whom there was angiographic and intravascular ultrasound evidence of an intraluminal thrombus overlying a small, nonocclusive plaque in an enlarged coronary artery.

Adult↗
PubMed1997

Atherosclerotic cardiovascular mortality during the 1992 riots in Los Angeles.

During the 3-day period of the Los Angeles riots in 1992, there was a significant increase in the total number of deaths investigated by the Coroner's office and deaths attributed to violence and trauma, but not to atherosclerotic cardiovascular mortality. However, there was a significant decrease in cardiovascular mortality in the period following the riots, compared with the period of the riots or the preceding period.

Arteriosclerosis↗
PubMed1997

Importance of the conal branch of the right coronary artery in patients with acute anterior wall myocardial infarction: electrocardiographic and angiographic correlation.

OBJECTIVES: This study assessed prospectively the correlation between the conal branch of the right coronary artery and the pattern of ST segment elevation in leads V1 and V3R during anterior wall acute myocardial infarction (AMI). BACKGROUND: The traditional electrocardiographic (ECG) definition of anteroseptal AMI-ST segment elevation in leads V1 to V3-has recently been challenged. The significance of ST segment elevation in lead V1 during anterior wall AMI is unclear. METHODS: The admission 12-lead ECG with additional lead V3R and the coronary angiograms performed within 10 days of hospital admission were evaluated in 28 consecutive patients (mean age +/- SD 62 +/- 9 years) admitted to the coronary care unit with anterior wall AMI. Patients were classified into two groups according to the magnitude of ST segment elevation in lead V1: group A (elevation > or = 1.5 mm, n = 12) and group B (elevation < 1.5 mm, n = 16). Two types of conal branch were identified: small (not reaching the interventricular septum [IVS]) and large (reaching the IVS). RESULTS: ST segment elevation in lead V3R was found in 11 (92%) and 6 (37%) patients from group A and group B, respectively (p < 0.001); a small conal branch was seen in 10 (83%) and 3 (19%) patients, respectively (p < 0.001). Ten patients (all from group B) had a large conal branch. CONCLUSIONS: ST segment elevation in lead V1 in the admission ECG of patients with anterior wall AMI is strongly related to ST segment elevation in lead V3R and is associated with a small conal branch. Our findings suggest that lead V1 reflects the right paraseptal area supplied by the septal branches of the left anterior descending coronary artery (LAD), alone or together with the conal branch. The absence of ST segment elevation in lead V1 during anterior AMI suggests that the IVS is protected by a large conal branch in addition to the septal branches of the LAD (double circulation).

Adult↗
PubMed1997

Abnormal Q waves on the admission electrocardiogram of patients with first acute myocardial infarction: prognostic implications.

BACKGROUND: Q waves developed in the subacute and persisting into the chronic phase of myocardial infarction (MI) usually signify myocardial necrosis. However, the mechanism and significance of Q waves that appear very early in the course of acute MI (< 6 h from onset of symptoms), especially if accompanied by ST elevation, are probably different. HYPOTHESIS: This study assesses the prognostic implications of abnormal Q waves on admission in 2,370 patients with first acute MI treated with thrombolytic therapy < 6 h of onset of symptoms. RESULTS: Patients with abnormal Q waves in > or = 2 leads with ST-segment elevation (n = 923) were older than patients without early Q waves (n = 1,447) (60.6 +/- 11.9 vs. 58.8 +/- 11.9 years, respectively; p = 0.0003), and had a greater incidence of hypertension (34.3 vs. 30.5%; p = 0.05) and anterior MI (60.6 vs. 41.1%; p < 0.0001). Time from onset of symptoms to therapy was longer in patients with Q waves upon admission (208 +/- 196 vs. 183 +/- 230 min; p = 0.01). Peak serum creatine kinase (2235 +/- 1544 vs. 1622 +/- 1536 IU; p < 0.0001), prevalence of heart failure during hospitalization (13.8 vs. 7.0%, p < 0.0002), hospital mortality (8.0 vs. 4.6%; p = 0.02), and cardiac mortality (6.6 vs. 4.5%, p = 0.11) were higher in patients with anterior MI and with abnormal Q waves than in those without abnormal Q waves upon admission. There was no difference in peak creatine kinase, prevalence of heart failure, in-hospital mortality, and cardiac mortality between patients with and without abnormal Q waves in inferior MI. Multivariate regression analysis confirmed that mortality is independently associated with presence of Q waves on admission (odds ratio 1.61; 95% CI 1.04-2.49; p = 0.04 for all patients; odds ratio 1.65; 95% CI 0.97-2.83; p = 0.09 for anterior wall MI. CONCLUSION: Abnormal Q waves on the admission electrocardiogram (ECG) are associated with higher peak creatine kinase, higher prevalence of heart failure, and increased mortality in patients with anterior MI. Abnormal Q waves on the admission ECG of patients with inferior MI are not associated with adverse prognosis.

Aged↗
PubMed1997

Differences in reperfusion length following 30 minutes of ischemia in the rabbit influence infarct size, as measured by triphenyltetrazolium chloride staining.

Assessment of myocardial infarct size in acute experimental models is usually done by triphenyltetrazolium-chloride (TTC) staining. A certain period of reperfusion is mandatory for discrimination of the infarct zone, especially after relatively short ischemic periods. However, it is unclear what the optimal reperfusion time is for full delineation of the infarct following 30 min of myocardial ischemia in the rabbit. This study compares infarct size, assessed by TTC, in anesthetized open-chest rabbits subjected to 30 min of coronary artery occlusion followed by either 2 (n = 14) v 4 (n = 14) (protocol 1), or 3 (n = 8) v 6 (n = 7) h of reperfusion (protocol 2). Area at risk was assessed by blue dye and necrotic zone by TTC staining. Protocol 1: heart rate and mean blood pressure were comparable in both groups throughout the protocol. Regional myocardial blood flows in both the ischemic and non-ischemic zones during ischemia and after 2 h of reperfusion were comparable between the groups. Regional myocardial blood flow in the post-ischemic zone deteriorated between 2 and 4 h (1.11 +/- 0.15 v 0.58 +/- 0.09 ml/min/g, respectively, P = 0.0004) of reperfusion. The size of the area at risk was comparable (0.31 +/- 0.03 v 0.33 +/- 0.03 of the LV weight in the 2 and 4 h reperfusion groups). However, the ratio of the necrotic zone to the ischemic zone at risk was 63% larger in the 4 compared to the 2 h of reperfusion group (0.31 +/- 0.04 v 0.19 +/- 0.05, respectively, P = 0.02). Analysis of covariance performed on the weight of tissue that developed necrosis and the weight of ischemic zone at risk revealed a significant effect of the reperfusion time (P = 0.014). Protocol 2: there was no difference in infarct size between rabbits subjected to three (0.38 +/- 0.05 of the area at risk) v 6 h (0.41 +/- 0.07) of reperfusion (P = 0.72). Analysis of covariance performed on the weight of tissue that developed necrosis and the weight of ischemic zone at risk did not reveal a significant effect of the reperfusion time. Infarct size as assessed by TTC following 30 min of myocardial ischemia, is smaller when measured 2 h after reperfusion than after 4 h of reperfusion. At least 3 h of reperfusion is needed to delineate infarct size by tetrazolium staining following 30 min of ischemia.

Animals↗
PubMed1997

The effect of CY1503, a sialyl Lewisx analog blocker of the selectin adhesion molecules, on infarct size and "no-reflow" in the rabbit model of acute myocardial infarction/reperfusion.

CY1503, an analogue of sialyl-Lewisx, is an inhibitor of the selectin adhesion molecules. CY1503 has been found to limit myocardial infarct size in canine and feline models. However, the effect of CY1503 on the "no-reflow" phenomenon is still unknown. Anesthetised rabbits were subjected to 30 min of coronary artery occlusion and 4 h of reperfusion. Protocol 1: after 27 min of ischemia, rabbits were randomised to an iv bolus of either CY1503 (30 mg/kg) (n=9) or saline (n=9). Protocol 2: rabbits were randomly given two iv boluses of CY1503 (30 mg/kg) (n=6) or saline (n=6), administered after 10 and 25 min of ischemia. Protocol 3: after 27 min of ischemia rabbits were randomly given an iv bolus of CY1503 (30 mg/kg) (n=6) and infusion of 20 mg/kg over 4 h or saline bolus+infusion (n=6). Regional myocardial blood flow (RMBF) was assessed after 30 min and 4 h of reperfusion. The risk zone (RZ) was assessed by blue dye and the necrotic zone (NZ) by tetrazolium staining. RMBF: protocol 1: RMBF in the RZ was 2.19+/-0.33 v 2. 34+/-0.34 ml/g/min in CY1503 and controls at 30 min (P=0.75), and 0. 43+/-0.07 v 0.41+/-0.08 at 4 h of reperfusion (P=0.85). The corresponding results for protocol 2 were 1.77+/-0.29 v 1.53+/-0.34 at 30 min (P=0.61) and 0.53+/-0.16 v 0.91+/-0.55 at 4 h (P=0.53). RMBF in RZ in protocol 3 were 1.52+/-0.25 v 1.32+/-0.20 at 30 min (P=0.56) and 0.30+/-0.05 v 0.29+/-0.09 (P=0.90) after 4 h of reperfusion. The RZ was similar in both groups in all protocols. The NZ/RZ ratio was comparable in the CY1503 and control group in all three protocols (0.32+/-0.04 v 0.37+/-0.06, 0.37+/-0.08 v 0.33+/-0. 07, and 0.51+/-0.05 v 0.38+/-0.05 in protocols 1, 2, and 3, respectively). CY1503 did not limit infarct size or prevent the "no-reflow" phenomenon in the rabbit.

Animals↗
PubMed1997

Changes in R wave amplitude: ECG differentiation between episodes of reocclusion and reperfusion associated with ST-segment elevation.

This study assesses the electrocardiographic (ECG) differences between episodes of increased ST-segment amplitude induced by coronary artery occlusion and by reperfusion in the open-chest rabbit model. Nine anesthetized open-chest male New Zealand White rabbits were subjected to four episodes of 5 minutes of coronary artery occlusion followed by 5 minutes of reperfusion. The ST-segment and R wave amplitudes were measured from an ECG lead attached to the pericardium overlying the ischemic myocardium. In 10 out of 35 (29%) of the episodes, reperfusion resulted in a transient increase in ST-segment amplitude. While episodes of coronary artery occlusion were associated with increase in R wave amplitude (69% and 97% of the episodes after 1 and 5 minutes, respectively), all reperfusion episodes were associated with prompt decrease in R wave amplitude. There was no difference between the repeated episodes in the occurrence of ST-segment elevation during reperfusion. However, ST-segment elevation during reperfusion could be distinguished from the ischemic episodes by the prompt decline in the R wave amplitude in the former compared with no change or increase in the latter.

Animals↗
PubMed1997

Juvenile ECG pattern in adult black Arabs.

A juvenile electrocardiographic (ECG) pattern is compatible with T wave inversion in the precordial leads V1 and V2 or in additional precordial leads to the left of V2. Electrocardiographic studies were performed in 48 Semitic Arabs, including 26 men and 22 women, and in 50 black Arabs (negroid Bedouins), including 22 men and 28 women. The subjects ranged in age from 20 to 46 years. The juvenile ECG pattern was found in 6 of the 28 black Arab women (21%), but it was not detected in the 22 black Arab men or in any Semitic Arabs of either sex. The difference between the two female groups was significant (P < .05). Careful interpretation of ECG recordings in black Arab women is recommended in order to prevent a misdiagnosis of myocardial ischemia or a misreading of T wave inversions related to a previous coronary event.

Adult↗