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Biomedical subjects

M M Laks

Publications and source records attributed to M M Laks.

At least 55 records · Page 3Linked to original sources
PubMed1988

Conventional and right precordial ECGs, creatine kinase, and radionuclide angiography in post-traumatic ventricular dysfunction.

Right ventricular infarction due to ischemic heart disease can be diagnosed by a right precordial electrogram or by first-pass radionuclide angiography (FPRNA). Prior FPRNA studies have shown that cardiac dysfunction after blunt chest trauma (myocardial contusion) is most often due to right ventricular dysfunction. We hypothesized that right ventricular dysfunction due to ischemic heart disease and myocardial contusion should produce similar ECG changes due to myocyte disruption. The purpose of our study was to evaluate the diagnostic value of the right precordial electrogram in suspected cardiac contusion. Thirty-five patients with suspected myocardial contusion based on mechanism of injury/clinical findings and no history of clinical heart disease were enrolled prospectively. All patients had conventional ECG, right precordial electrogram, and FPRNA studies. Twenty patients had normal cardiac scans (group 1); percentage of myocardial creatine kinase (CK-MB) was measured in 12 of these patients and was less than 5% in 11. Fifteen patients had abnormal cardiac scans (wall motion abnormality and/or decreased right ventricular ejection fraction) (mean, 34% +/- 7% [SD]; normal, greater than 40%) (group 2); percentage of CK-MB was measured in 13 of 15 patients and was less than 5% in all 13. Conventional ECGs and right precordial electrograms in all patients were analyzed for differences in heart rate, PR interval, QRS duration, corrected QT interval, and the axis of the frontal and horizontal plane QRS complex and ST segment. There were no significant differences between group 1 and group 2 patients. No patient with myocardial contusion diagnosed by FPRNA had elevated ST segments in V4R through V6R or a percentage CK-MB of more than 5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

A new technique for producing myocardial infarction using coronary artery balloon occlusion.

Many techniques for producing myocardial infarction have required the potential physiological altering effects of a thoracotomy. Previous techniques have used the variable and therefore unpredictable effects of coronary artery injection of occlusive agents, intravascular plugs, and externalized coronary balloon catheters. Previous investigators have reported a survival rate of 50-70%. In the present study a new closed chest dog technique was used in which a catheter with an inflatable detachable balloon was placed in the aorta via the carotid artery. The catheter could be readily lodged into any portion of the right, left anterior, or circumflex coronary artery. The proximal left anterior descending and circumflex arteries were occluded in 15 dogs. This new coronary artery balloon occlusion technique may be used to produce a chronic myocardial infarction with a high survival rate of 90% through the use of short acting anaesthesia and rapid reversal of the effect of morphine with naloxone hydrochloride. The rapid recovery of the dog permits earlier study of haemodynamic variables and arrhythmia due to myocardial infarction in the best physiological state.

Animals↗
PubMed1987

Esophageal electrocardiography in acute cardiac care. Efficacy and diagnostic value of a new technique.

Esophageal electrocardiography can detect atrial electrical activity during tachyarrhythmias when P waves are not evident by surface electrocardiography. However, patient discomfort, the difficulty of accurately interpreting cardiac signals against a background of electrical noise, and the complexity of use have limited widespread application. In this study, esophageal electrocardiography was used in 48 acutely ill patients with a new "pill electrode" system, consisting of a bipolar electrode pair (3 by 20 mm) attached to 0.5 mm diameter Teflon wires contained in a standard gelatin capsule. The capsule with enclosed electrodes was voluntarily swallowed, and the recording electrodes were positioned posterior to the left atrium. A preamplifier system with a low-frequency filter and a standard three-channel electrocardiographic recorder were used. Esophageal "pill" electrocardiographic recordings were made in 48 of 50 eligible study patients (96 percent) with tachyarrhythmias and absent or equivocal atrial activity on surface electrocardiography. In these patients, a high-quality esophageal electrocardiographic recording was obtained within one to 10 minutes with minimal patient discomfort. In 25 of 48 study patients (52 percent), the original diagnosis, based on the surface electrocardiographic recording, was incorrect after review of the esophageal recording. Results of esophageal recording altered management in 19 of 48 (40 percent) patients. This new and simple technique facilitates diagnosis and management of perplexing tachyarrhythmias in acutely ill patients by physicians with minimal training in the technique.

Acute Disease↗
PubMed1987

Electrocardiographic diagnosis of left ventricular hypertrophy in the presence of left bundle branch block.

The electrocardiographic diagnosis of LVH in the presence of LBBB has previously been difficult. Thirty-seven patients with complete LBBB were identified and had echocardiography performed. Using an accepted echocardiographic formula, left ventricular mass was calculated. Twenty of the 37 patients (54%) were classified as having severe LVH. Multiple conventional ECG criteria for LVH were then evaluated. No QRS voltage criteria showed any difference between patients with and without LVH (P = NS). There was also no correlation between either QRS axis or left atrial enlargement and left ventricular mass (P = NS). However, the QRS duration was significantly longer in the patients with LVH (160 +/- 12 msec) than in the normal patients (148 +/- 11 msec) (P less than 0.001). The sensitivity, specificity, positive predictive value, and accuracy of several voltage criteria and QRS duration were examined. The best voltage criteria had a sensitivity of only 50% and a predictive value of 63%. However, a QRS duration greater than 155 msec had a sensitivity of 60% and a predictive value of 82%. This study demonstrates that the conventional QRS voltage criteria for LVH are not accurate in LBBB. A relationship exists between increasing QRS duration in LBBB and LVH; therefore, the relative probability adjectives: "consider," "possible," and "probable" should be used. QRS duration greater than 155 msec is predictive of LVH despite the presence of LBBB.

Adult↗
PubMed1987

Early experience with esophageal pill electrode atrial pacing in the diagnosis of coronary artery disease--a trend toward improved specificity compared to treadmill exercise.

Esophageal pill electrode pacing, treadmill exercise and coronary angiography were performed in 23 patients with chest pain. Atrial pacing produced fewer false positive studies resulting in higher specificity compared to treadmill exercise. Some possible explanations of the improved specificity are the better quality tracings obtained with atrial pacing and the increased control of the heart rate and blood pressure response during atrial pacing as opposed to treadmill exercise. This preliminary study suggests that esophageal pill electrode atrial pacing tachycardia studies may be a reasonable alternative to treadmill exercise testing in the noninvasive diagnosis of coronary artery disease.

Adult↗
PubMed1987

A technique to evaluate the performance of computerized ECG analysis systems.

No objective method to test computerized ECG systems has been available. Until now, tests have been conducted separately for instrumentation and algorithms. Hence, to facilitate objective verification and testing of modern computerized ECG equipment, a dedicated high resolution, low noise instrument (an "electronic test patient") has been developed. The purpose of this communication is to describe this new instrument and its electrocardiographic database. The instrument is designed not to cause any disturbances to the original ECG signals in the frequency range from 0 to 1 kHz. The input channels accommodating standard 12-lead and 3-lead Frank systems are sampled simultaneously at 10 kHz each with 90 dB dynamic range. The overall RMS noise figure of the instrument is 1 microV. The integral part of the instrument is a high resolution, high bandwidth minidatabase consisting of selected A-type and B-type verified electrocardiograms such as infarctions, ventricular hypertrophies, atrial fibrillations, etc. The minidatabase was collected with the aid of a computerized ECG system, which has a program for searching for specific electrocardiographic diagnosis. Each database record consists of simultaneous electrocardiographic signals of all standard leads and Frank leads, and a validated diagnostic report. A system under test is typically connected via its patient cable to the analog output of the instrument. The testing is performed with reference to the validated ECG from the database. In that way, our minidatabase is compatible with any electrocardiographic system. The only similar database assembled for testing purposes is that of the CSE group.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Systems↗
PubMed1986

Electrocardiographic criteria for tricyclic antidepressant cardiotoxicity.

To determine if electrocardiographic findings characterize tricyclic antidepressant (TCA) overdose and cardiotoxicity, 25 patients suspected of taking an overdose of TCA were studied. Toxicologic assays for a TCA were positive in 11 patients (+TCA, n = 11). Toxicologic study results for a TCA were negative in 14 patients (-TCA, control subjects). Patients with positive TCA results (+TCA) had a significantly greater heart rate (117 +/- 23 vs 100 +/- 22 beats/min, p less than 0.05), QRS duration (103 +/- 15 vs 87 +/- 10 ms, p less than 0.005) and corrected QT interval (449 +/- 38 vs 418 +/- 36 ms, p less than 0.05) than control patients (-TCA) on admission. Patients with positive TCA results also had a more rightward terminal 40-ms frontal plane QRS vector (195 +/- 51 degrees vs 54 +/- 64 degrees, p less than 0.001) than control patients. This observation has not been previously reported. A terminal QRS vector of 130 degrees to 270 degrees accurately discriminated between -TCA and +TCA patients (positive and negative predictive value = 1.00). Counterclockwise rotation (normalization) of the terminal frontal plane QRS vector was noted in +TCA patients during hospitalization. All +TCA patients had a sinus tachycardia, a corrected QT interval 418 ms or longer, and a terminal QRS vector between 130 degrees and 270 degrees. Using these values as selection criteria, a computer-aided search of 15,064 electrocardiograms (ECGs) recorded in our emergency department was performed. The likelihood of encountering such an electrocardiographic pattern in this population was 1.0%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Quantitative analysis of segmental wall motion during maximal upright dynamic exercise: variability in normal adults.

Twenty-five healthy adults underwent subcostal-view, four-chamber two-dimensional echocardiographic examination while upright at rest and at the peak of maximal bicycle exercise. The purpose of the study was to determine whether the variability in regional left ventricular endocardial motion, previously demonstrated to be present at rest, persisted at peak exercise. The rest and exercise end-diastolic and end-systolic endocardial contours were visually identified, digitized, and divided into 32 radial segments after realignment by the computer. At rest there was similar percent segmental area reduction for the septum (segments 1 to 12) (54 +/- 4%, mean +/- 1 SD), apex (segments 13 to 20) (67 +/- 3%), and lateral wall (segments 21 to 32) (67 +/- 8%). At peak exercise the percent area reduction increased significantly: septum 84 +/- 5%, apex 88 +/- 2%, lateral wall 83 +/- 6% (p less than .001 compared with rest for all areas). However, there was considerable variability in percent area reduction between different radial segments in the same individual. At rest the difference between minimal and maximal percent area reduction within the same individual was 49 +/- 17 percentage units (range 21 to 83) and that at peak exercise was 32 +/- 17 percentage units (range 0 to 66). It is concluded that, because the range of standard deviation of normal endocardial motion and the degree of variability between radial segments in the same healthy individual are significant, qualitatively determined "hypokinesis," as commonly assessed clinically, may be a normal event. However, segmental akinesis or dyskinesis, which occurred rarely at rest and never at peak exercise, must be considered abnormal events.

Adolescent↗
PubMed1986

Yield of endomyocardial biopsy in patients with biventricular failure. Comparison of patients with normal vs reduced left ventricular ejection fraction.

Twenty five patients with biventricular failure underwent endomyocardial biopsy procedures. Twelve of these 25 patients had normal left ventricular ejection fraction. Endomyocardial biopsy sampling was useful in eight of 12 patients (67 percent) with biventricular failure and normal left ventricular ejection fraction. Biopsy specimens in five of these 12 patients demonstrated endocardial or infiltrative heart disease and excluded these diseases in three other patients with constrictive pericarditis. This study suggests that the clinical presentation of biventricular failure, combined with the noninvasive determination of a normal left ventricular ejection fraction, is helpful in selecting patients for endomyocardial biopsy study. Patients with biventricular failure and normal left ventricular ejection fractions have a high probability of having pericardial or infiltrative heart disease, conditions that often can be differentiated only by analysis of myocardial tissue. Hemodynamic assessment of patients without infiltrative processes further allows one to eliminate those patients with a high likelihood of having constrictive pericardial disease.

Adolescent↗
PubMed1985

Mitral valve prolapse in sickle cell disease: manifestation of a generalized connective tissue disorder.

Previous studies have shown an association of sickle cell disease with generalized connective tissue disorders such as pseudoxanthoma elasticum. We recently documented an unexpectedly high prevalence of mitral valve prolapse, a connective tissue disorder, in sickle cell disease. To investigate this association, skin biopsies were analyzed from 32 sickle cell disease patients, 11 of whom had mitral prolapse. Total and type III collagen, collagen solubility, and uronic acid were not different between the patients with or without mitral prolapse (p greater than 0.05). Computerized morphometric quantitation of the volume fraction of elastic fibers was greater in sickle cell disease patients than in 10 normals (3.1 +/- 0.1 mean +/- SEM vs 2.0 +/- 0.3%; p less than 0.01) but less than in three patients with pseudoxanthoma elasticum (9.7 +/- 0.6%; p less than 0.001). Desmosine radioimmunoassay (an index of elastic fibers) was greater in sickle cell disease patients with mitral prolapse than those without (239.3 +/- 9.3 vs 171.7 +/- 25.4 ng/mg wet weight; p less than 0.02). Histopathologic grading showed a similar trend (p = 0.07). The combined probabilities of these three independent tests of elastic fiber quantity showed an increased elastic fiber concentration in mitral prolapse patients compared to those without mitral prolapse (p less than 0.02). Thus, there is no evidence for a specific collagen defect; rather, sickle cell disease appears to be associated with a spectrum of elastic tissue disorders, a feature that could predispose to mitral valve prolapse.

Adolescent↗
PubMed1985

Stress ventricular function test in conscious, nonthoracotomised dogs to assess cardiac drug efficacy.

The measurement of left ventricular (LV) function is frequently performed in unconscious or thoracotomised animals in the resting state; these conditions may seriously affect the basal haemodynamic state. To assess myocardial function in conscious animals, a technique was developed to place a catheter across the atrial septum into the left ventricle without a thoracotomy. A stress ventricular function test (SVFT) was performed by raising the systemic blood pressure with methoxamine in the conscious dog. In order to demonstrate the effectiveness of the SVFT in the detection of a decrease in ventricular function, a SVFT was performed before and after the acute infusion of verapamil to determine resting and reserve LV function. A slope relating systolic aortic pressure to the LV end-diastolic pressure was obtained in 10 dogs using a low dose (0.005) and in four dogs a high dose (0.01 microgram X kg-1 X min-1) verapamil (V). The mean slope before V was 3.6 +/- 1.2 and after 2.0 +/- 0.92 (p less than 0.001). The day-to-day variability of the SVFT was less than 22% (coefficient of variability). The SVFT is a sensitive, reproducible method to assess resting and increased or decreased myocardial contractility and is useful in selecting appropriate doses of cardiac drugs to determine their effect on the myocardium during acute and chronic infusion studies in the conscious, nonthoracotomised dog.

Animals↗
PubMed1985

New implanted chronic catheter device for determining blood pressure and cardiac output in conscious dog.

The Vascular-Access-Port (VAP) is a subcutaneous implantable device designed for repeated venous blood sampling in humans. With slight modifications the device has been used in the arterial and venous systems of dogs. This device allows for chronic repeated arterial blood pressure monitoring, monitoring of cardiac outputs, and blood sampling in conscious dogs. Infection, vascular thrombosis, and catheter extraction have not occurred. This modified VAP has been used for 6 mo and in 25 dogs to date without any failure to determine arterial blood pressure and cardiac output.

Animals↗
PubMed1985

Reversal of reflex pulmonary vasoconstriction induced by main pulmonary arterial distension.

Distension of the main pulmonary artery (MPA) induces pulmonary hypertension, most probably by neurogenic reflex pulmonary vasoconstriction, although constriction of the pulmonary vessels has not actually been demonstrated. In previous studies in dogs with increased pulmonary vascular resistance produced by airway hypoxia, exogenous arachidonic acid has led to the production of pulmonary vasodilator prostaglandins. Hence, in the present study, we investigated the effect of arachidonic acid in seven intact anesthetized dogs after pulmonary vascular resistance was increased by MPA distention. After steady-state pulmonary hypertension was established, arachidonic acid (1.0 mg/min) was infused into the right ventricle for 16 min; 15-20 min later a 16-mg bolus of arachidonic acid was injected. MPA distension was maintained throughout the study. Although the infusion of arachidonic acid significantly lowered the elevated pulmonary vascular resistance induced by MPA distension, the pulmonary vascular resistance returned to control levels only after the bolus injection of arachidonic acid. Notably, the bolus injection caused a biphasic response which first increased the pulmonary vascular resistance transiently before lowering it to control levels. In dogs with resting levels of pulmonary vascular resistance, administration of arachidonic acid in the same manner did not alter the pulmonary vascular resistance. It is concluded that MPA distension does indeed cause reflex pulmonary vasoconstriction which can be reversed by vasodilator metabolites of arachidonic acid. Even though this reflex may help maintain high pulmonary vascular resistance in the fetus, its function in the adult is obscure.

Animals↗
PubMed1985

Abnormal septal Q waves in sickle cell disease. Prevalence and causative factors.

Electrocardiograms and M-mode echocardiograms were obtained prospectively from 72 patients with hemoglobin SS (n = 55) or SC (n = 17) disease to assess the prevalence of abnormal Q waves in sickle cell disease and to determine if such Q waves could be explained by, or related to, echocardiographically determined anatomic or functional abnormalities. The mean age (+/- SD) of the population under study was 28 +/- 9 years, and the mean hematocrit reading was 28 +/- 5 percent; 43 male and 29 female patients were evaluated. No patient had a history of systemic arterial hypertension, valvular heart disease, or congestive heart failure. Abnormal septal Q waves (amplitude greater than or equal to 0.30 mV; duration less than or equal to 29 msec) were noted in leads V4, V5, or V6 in 15 of 72 patients, and 50 percent (36) of the population under study demonstrated electrocardiographic voltage changes consistent with left ventricular hypertrophy. M-mode echocardiography showed that 29 of 72 patients had a thickened interventricular septum (greater than or equal to 1.2 cm), 16 of 72 had an abnormally thickened left ventricular posterior wall (greater than or equal to 1.2 cm), and 31 of 72 had increased left ventricular mass (greater than 215 g). The prevalence of electrocardiographic and echocardiographic abnormalities was not significantly different between patients with hemoglobin SS and SC disease. Septal excursion was decreased in 11 of the patients, and global left ventricular function (percent fractional shortening) was slightly decreased in three patients. Regional wall motion was normal in all 72 patients. Six percent (four) of the patients met echocardiographic criteria for asymmetric septal hypertrophy. Linear regression analysis yielded significant positive correlations between septal dimension (r = 0.38; p less than 0.001) and left ventricular mass (r = 0.37; p less than 0.005) when each was compared with Q-wave amplitude. A significant negative correlation (r = 0.40; p less than 0.001) was noted between hematocrit reading and Q-wave amplitude. We conclude that abnormal septal Q waves are common in sickle cell disease and are related, in part, to septal thickness, as well as left ventricular mass and degree of anemia.

Adolescent↗
PubMed1985

Mitral valve prolapse in sickle cell disease. Presumptive evidence for a linked connective tissue disorder.

To determine the prevalence of mitral valve prolapse in sickle cell disease, M-mode echocardiography was performed on 57 patients with sickle cell disease and 35 patients with chronic anemia of end-stage renal disease (anemic control group). In 25% (14/57) of patients with sickle cell disease, unequivocal mitral valve prolapse was diagnosed by echocardiography; all these patients had a mobile systolic click and/or late systolic murmur. This figure was significantly greater than the reported 5% to 6% prevalence in the general adult population, the 1% to 3% prevalence in the black population, and the 3.0% prevalence (1/35) in the anemic control group. The association of mitral valve prolapse and sickle cell disease cannot be explained on the basis of left ventricular size, systolic function, ischemic left ventricular or papillary muscle dysfunction, or chronic anemia. Therefore, a linked connective tissue defect in these two diseases is a hypothesis worthy of further investigation.

Adolescent↗