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Biomedical subjects

J L Vacek

Publications and source records attributed to J L Vacek.

At least 55 records · Page 3Linked to original sources
PubMed1992

Slowing of ventricular tachycardia as a possible endpoint for serial drug testing at electrophysiological study.

Certain patients who cannot be rendered noninducible by serial drug testing during electrophysiology study demonstrate significant slowing of their ventricular tachycardia rate with selected agents. We evaluated the characteristics and outcome of 19 such patients to assess whether this slowing could be considered an acceptable endpoint for treatment. This group consisted of 14 males and 5 females (mean age 63 +/- 9) with a mean ejection fraction of 28 +/- 13% and inducible sustained ventricular tachycardia. Sixteen patients had known coronary artery disease and 13 had prior myocardial infarction. The other three patients had idiopathic cardiomyopathy. Serial drug testing during an electrophysiology protocol that used up to three extrastimuli at two or three cycle lengths at two right ventricular sites was used to select a medication regimen that provided optimal ventricular tachycardia slowing without limiting side effects. Five patients were treated with amiodarone, three with Ic agents (all with ejection fraction greater than 30%), and the remainder with Ia and Ib agents alone or in combination. Mean initial ventricular tachycardia rate was 219 +/- 26 beats/min with posttreatment ventricular tachycardia rate 137 +/- 17 (mean initial cycle length 278 +/- 35 msec, posttreatment 443 +/- 53 msec). Two groups were identified, those who had recurrent (although well-tolerated) ventricular tachycardia (group I, n = 8, mean time to recurrence = 15 months), and those who did not (group II, n = 11, mean follow-up 22 months). Overall sudden death rate was 5%, while total mortality was 11% (all mortality in group I).(ABSTRACT TRUNCATED AT 250 WORDS)

Amiodarone↗
PubMed1992

Anticoagulant effect of iohexol vs. ioxaglate during cardiac catheterization.

Contrast agent safety during cardiac catheterization (CC) may relate in part to anti- or procoagulant effect. We studied these effects in 177 patients who underwent standard CC (N=112) or percutaneous transluminal coronary angioplasty (PTCA) (N=65) and received either iohexol (N=111) or ioxaglate (N=66). Patients received either 0 or 2000u heparin for CC or 10,000u for PTCA. The groups were similar in regards to age, sex, amount of contrast used, and procedure time. Partial thromboplastin time (PTT) and activated clotting time (ACT) were both significantly increased (P less than .01) in patients who received 10,000u heparin irrespective of type of contrast agent although larger increases were seen in the iohexol group. With 2000u of heparin, ACT and PTT increased significantly (P less than .01) only in the iohexol group. PTT and ACT actually decreased to similar and significant (P less than .01) degrees after both iohexol and ioxaglate when heparin was not used. We conclude: 1) commonly used measures of anticoagulant (ACT and PTT) show greater prolongation after either 2000 or 10,000u of heparin with iohexol than ioxaglate, 2) ACT and PCT appear to shorten with both iohexol and ioxaglate if no heparin is used. This data would suggest that ioxaglate does not have an anticoagulant advantage over iohexol.

Aged↗
PubMed1991

Lack of reproducibility of frequency versus time domain signal-averaged electrocardiographic analyses and effects of lead polarity in coronary artery disease.

Time domain signal-averaged electrocardiographic parameters have been found to be consistent over the short term. Similar data have not been verified for the frequency domain. In addition, the effects of lead polarity changes on time domain or frequency domain parameters are not known. Signal-averaged electrocardiography was performed on 15 patients using the Arrhythmia Research Technology model 1200 EPX with orthogonal X, Y and Z leads. Time domain variables included filtered QRS, root-mean-square voltage of the last 40 ms of the QRS and duration of signals less than 40 microV. Two frequency domain area ratios were analyzed: a 140-ms window including last 40 ms of QRS + 100 ms of ST; and a 140-ms window beginning at QRS onset (both 20 to 50/0 to 20 Hz). Values were compared for each lead, as well as for a vector composite and the arithmetic mean of the 3 leads. Each patient underwent 3 studies performed 5 minutes apart. The polarity of the X lead was reversed between the first and second studies, and then returned to standard for the third study. Time domain variables correlated closely among the studies irrespective of lead polarity, with r values of 0.993 to 1.000 (p less than 0.0001). Frequency domain parameter correlation was much poorer, with r values as low as 0.276. Frequency domain correlations between tests 1 and 2 and 2 and 3 (mean r = 0.778) were poorer than between tests 1 and 3 (mean r = 0.829), implying an effect of lead polarity change.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Exercise echocardiography as a screening test for coronary artery disease and correlation with coronary arteriography.

We evaluated exercise echocardiography as a screening test for coronary artery disease in 228 patients, all of whom underwent subsequent coronary angiography. After an echocardiogram at rest was obtained, each patient performed maximal, symptom-limited, upright treadmill exercise, immediately after which repeat imaging was performed. The exercise echocardiogram was abnormal if any segment failed to become hypercontractile with exercise, and these regional wall motion abnormalities were used to predict the extent and distribution of coronary disease. At subsequent angiography, coronary stenosis was defined as significant if luminal diameter was reduced greater than or equal to 50%. Compared with electrocardiography, exercise echocardiography was more sensitive (97 vs 51%) and specific (64 vs 62%), and had higher positive (90 vs 82%) and negative (87 vs 28%) predictive accuracies. Exercise echocardiography was also highly predictive of the extent (no, 1-, 2- or 3-vessel disease) and distribution (which vessel) of coronary stenoses. It is concluded that exercise echocardiography is an excellent screening test for the presence, extent and distribution of coronary artery disease.

Constriction, Pathologic↗
PubMed1991

Prognosis of culprit lesion PTCA in acute myocardial infarction for multi versus single vessel disease.

UNLABELLED: We studied 417 patients undergoing single vessel culprit lesion percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction to determine the impact of disease in other vessels. Group A (189 patients, 45%) had coronary artery disease (greater than or equal to 70% stenosis) in at least 1 additional vessel while Group B (228 patients, 55%) did not. The groups were similar in sex distribution (A = 75% male, B = 76%), number of lesions in the single culprit vessel dilated (1 lesion in 83% A, 80% B), and PTCA success (A = 92%, B-94%) (all p = NS). Group A patients were older (63 +/- 10 vs. 56 +/- 11 years) and had more prior myocardial infarctions (27% vs. 7%), and more prior coronary artery bypass grafting (15% vs. 0.4%) (all p less than .01). Group A patients were more likely to have repeat catheterization (48% vs. 32%, p less than .005) although restenosis of the infarct-related vessel was similar (A = 24%, B = 16%) (p = NS). Group A was more likely to need angioplasty in a 2nd vessel (23% vs. 8%) and to need coronary artery bypass grafting (20% vs. 8%) (both p less than .001). Cumulative mortality was higher in Group A at 1 month (10% vs. 5%), 1 year (11% vs. 6%), and long-term (13% vs. 7%). This difference appeared to be due to the impact of lower mean ejection fraction in Group A. CONCLUSION: Treatment of acute myocardial infarction by direct PTCA of the culprit lesion can be performed with a high likelihood of success in patients with or without multivessel coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Mexiletine effects on theophylline disposition.

The effect of mexiletine administration on steady-state plasma theophylline concentrations was studied in eight normal healthy men in a prospective open label nonrandomized two-way crossover trial. Repeated doses of 300 mg of sustained-release theophylline were given every 12 hours for 9 days. Mexiletine hydrochloride, 200 mg every 8 hours, was given for five consecutive doses starting on the morning of day 6. Mexiletine increased theophylline levels in all subjects. Mean predose (trough) levels rose from 8.1 +/- 0.1 microgram.ml-1 to 13.4 +/- 0.6 micrograms.ml-1 and AUC(0-12) from 96.8 +/- 9.1 to 160.2 +/- 3.7 micrograms.ml-1.hr. Plasma clearance was reduced by mexiletine from 44.7 +/- 5.1 to 25.4 +/- 1.2 ml.hr-1. Both N-demethylated metabolites of theophylline were decreased by 60% by mexiletine, whose levels remained within its therapeutic range. Theophylline levels returned to pre-mexiletine values when this drug was discontinued. Mexiletine reduces theophylline clearance and increases its plasma concentration by inhibiting N-demethylation of theophylline. Plasma theophylline levels should be monitored when mexiletine is added.

Adult↗
PubMed1991

Diagnosing syncope. With an emphasis on cardiac causes.

Evaluation of syncope may be lengthy and expensive, and, in up to 50% of patients, will not produce a diagnosis. If a definite cause is found, specific therapy may offer symptomatic relief, although the patient's prognosis depends primarily on the nature and severity of any underlying disease. A patient with no evidence of organic heart disease for whom a complete evaluation reveals no cause for syncope has an excellent prognosis, even though syncopal symptoms may recur. The initial evaluation and management of most patients with syncope can be performed by the primary care physician if facilities for Holter monitoring, echocardiography, and signal-averaged electrocardiography are available. Consultation with a cardiologist is necessary only when the results of the initial evaluation are unrevealing or if findings suggest the need for a more intensive secondary elevation.

Cardiovascular Diseases↗
PubMed1991

The effects of smoking on the signal-averaged electrocardiogram in normal subjects.

Tobacco smoking increases the risk of sudden cardiac death, possibly by altering the substrate for propagation or sustainment of ventricular tachyarrhythmias. To test this hypothesis, 15 long-term smokers without known coronary artery disease abstained from tobacco smoking for 12 h, after which they underwent SAECG before, 15 min after and 30 min after smoking two cigarettes. Other than minor lengthening of filtered QRS duration, no significant change in time-domain SAECG parameters was noted. We conclude that late potentials are not produced by cigarette smoking and that ventricular arrhythmia substrate as measured by SAECG variables is not worsened in long-term smokers without evidence of coronary artery disease.

Adult↗
PubMed1991

The use of percutaneous transluminal coronary angioplasty in myocardial infarction.

To evaluate the effectiveness of percutaneous transluminal coronary angioplasty (PTCA) in the treatment of myocardial infarction, we reviewed the records of 508 consecutive patients treated within 6 hours of pain onset. Two hundred fifty-eight patients received direct PTCA without thrombolytic therapy, and 250 received thrombolytic therapy followed by immediate PTCA (within 24 hours, n=73) or delayed PTCA (later than 24 hours, n=177). The direct-PTCA group had the lowest initial success rate (92%) and the highest 1-week (8.1%) and 1-year (14%) mortality rates. Immediate PTCA had a 96% success rate, and 6.8% 1-week and 8.2% 1-year mortality rates. Delayed PTCA had the same initial success (96%), but lower 1-week (1.7%) and 1-year (2.3%) mortality. We conclude that both direct PTCA and combination treatment (thrombolytic therapy followed by PTCA) result in high rates of recanalizing occluded coronary arteries, but that combination treatment has higher initial success and survival rates, with delay in the use of PTCA producing the best survival rates.

Journal Article↗
PubMed1990

Management comparison for acute myocardial infarction: direct angioplasty versus sequential thrombolysis-angioplasty.

To compare the results and outcome of different management approaches for acute myocardial infarction, we analyzed our experience with early (i.e., within 6 hours of infarct onset) direct percutaneous transluminal coronary angioplasty (group A) versus initial treatment with thrombolytic therapy (group B) followed by angioplasty. From 1982 to 1989 a total of 214 patients underwent primary angioplasty for acute myocardial infarction. During this time 157 patients underwent initial thrombolytic therapy, 104 with intravenous streptokinase and 53 with intravenous tissue-type plasminogen activator followed by angioplasty. Other than age (group A, 61.7 +/- 11.5 years; group B, 57.3 +/- 11.6 years; p = 0.0002), the clinical characteristics of the groups were similar. In group A, 197 (92.1%) had successful results, and 17 (7.9%) were failures. Of the group treated with thrombolytic therapy, there was an overall 81.5% patency rate for patients treated with streptokinase and tissue-type plasminogen activator with no significant difference between the agents. Angioplasty success after thrombolytic therapy was 94.3%. In-hospital and 1-year survival was significantly better in group B patients (95.5% and 95.5%, respectively) than in group A patients (92.1% and 89.3%, respectively). We conclude that both direct angioplasty and thrombolytic therapy followed by angioplasty provide high recanalization rates but that short- and long-term survival is improved when thrombolytic therapy precedes angioplasty in acute myocardial infarction patients.

Aged↗
PubMed1990

Techniques for the determination of left ventricular mass by signal-averaged electrocardiography.

UNLABELLED: The standard ECG correlates poorly with LV mass. The SAECG precisely measures myocardial energy and may allow more exact noninvasive assessment of LV mass. A commercially available system (Corazonix Predictor I) was tested for its ability to reproduce and measure known input energy in square wave and QRS waveforms, using frequency bandwidths different from those used for late potential analysis. A test group of 15 patients was studied to determine optimum filter type and bandwidth for comparison of SAECG energy measurement versus LV mass as determined by echocardiography (Penn conversion) and LV hypertrophy via standard ECG criteria. The best means of energy measurement were maximum and total RMS voltage and the integral of the area under the QRS curve. Optimum correlation with echocardiography was seen with a bidirectional band-pass filter of 5 to 250 Hz applied either to the vector sum of the three orthogonal leads or to the Z lead alone (r values 0.61 to 0.73), which was equal to or superior to standard ECG LV hypertrophy determinants. A second group of 20 patients was studied prospectively to confirm these findings, which yielded similar results. CONCLUSION: (1) the SAECG when appropriately modified serves as a rapid noninvasive assessment of LV mass. (2) These modifications must examine the entire duration and energy spectrum of the surface ECG and not just the region of late potentials. (3) Very low frequencies (below 5 Hz) must be excluded to eliminate the energy present due to DC offset voltage.

Cardiomegaly↗
PubMed1990

Echocardiography. Basics for the primary care physician.

Echocardiography is commonly performed to assess aortic stenosis, mitral valve prolapse, pericardial effusion and cardiac tamponade, myocardial infarction, endocarditis, and valvular regurgitation. We have found that the more defined and appropriate a request for an echocardiogram is, the better the technician and interpreter can relate observations to the requesting physician. Thus, thorough understanding of the indications and limitations of echocardiography by the primary care physician will result in improved patient care.

Aortic Valve Stenosis↗