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Biomedical subjects

M H Ellestad

Publications and source records attributed to M H Ellestad.

At least 19 recordsLinked to original sources
PubMed1992

Analysis of the signal-averaged P-wave duration in patients with percutaneous coronary angioplasty-induced myocardial ischemia.

To assess the impact of angioplasty-induced myocardial ischemia on the duration of the surface P wave, patients undergoing elective angioplasty of isolated lesion in the left anterior descending, circumflex or right coronary arteries were monitored with a 3-channel electrocardiographic Holter system. The leads used were modified bipolar chest leads V5, aVF and V2 (CM-V5, CS-aVF and CM-V2). After echocardiographic signal-averaging, the earliest onset and the latest offset of the P wave were identified in all of the above time-aligned signal-averaged leads, and the composite maximal P duration was measured under 10 x magnification. The maximal ST-segment shift during balloon inflation was also measured in all of the above leads at 60 ms after the J point. In the study group comprising 47 patients, the mean signal-averaged P-wave duration was 125.0 +/- 16 ms at baseline versus 130.0 +/- 15 ms during balloon inflation, p less than 0.005. In the left anterior descending coronary artery group (n = 23), the mean signal-averaged P-wave duration was 122.4 +/- 17 ms and 131.3 +/- 16 ms during balloon inflation, p less than 0.005). In the group with a right coronary artery lesion (n = 18), the values were 127.3 +/- 14 ms and 128.4 +/- 13 ms respectively (p = not significant). Significant increases in the P-wave duration were found to occur in groups both with (n = 34) and without (n = 13) ST-segment shift greater than or equal to 1 mm (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1992

Efficacy of three-channel ambulatory electrocardiographic monitoring for the detection of myocardial ischemia.

The recognition of silent myocardial ischemia (SMI) has been demonstrated to have important clinical relevance. Two-channel ambulatory (Holter) electrocardiographic recording is a commonly utilized method for detecting transient electrocardiographic ST segment changes representative of SMI. It has been suggested that the analysis of two channels alone may not adequately detect SMI. We therefore evaluated the diagnostic yield of three channels using a three-channel electrocardiographic monitoring device in 46 consecutive patients (age 61 +/- 9 years) undergoing percutaneous transluminal coronary angioplasty of an isolated single-vessel stenosis. Modified bipolar chest leads V2, V5, and AVF (CM-V2, CM-V5, and CS-AVF) were utilized for analysis. The percent detection of ST segment changes from various combinations of two-lead recordings were compared to the total three leads, and an absolute transient ST segment shift (STSS) of greater than or equal to 1 mm during balloon inflation was considered as evidence of myocardial ischemia. One patient was excluded because of the need for ventricular pacing during balloon inflation. A total of 33 of 45 patients had STSS in all three leads (percent detection = 73%), while 32 (71%) had STSS in the two-lead grouping with the highest diagnostic yield (CM-V2/CM-V5; p = ns). Of the various two-lead combinations studied, leads CM-V2 and CM-V5 provided the best lead set overall for the detection of ischemic STSS. Three-channel ambulatory electrocardiographic recording only marginally improves upon the detection of ischemia when compared with standard (CM-V2/CM-V5 or CM-V5/CS-AVF) two-channel ambulatory electrocardiographic recordings.

Angioplasty, Balloon, Coronary↗
PubMed1992

The predictive value of the time course of ST segment depression during exercise testing in patients referred for coronary angiograms.

We studied the time course of ST segment depression during and after exercise testing in 462 subjects who also had coronary angiograms. Sixty-three percent of patients with late onset-early offset ST depression, previously reported to be likely to have false positive tests, had significant coronary artery disease, and 32% had three-vessel disease. Those with early onset and late offset ST depression and those with resting ST depression that was accentuated with exercise had a high prevalence of significant coronary artery disease and three-vessel disease. We found that observation of the time course of ST depression during and after exercise adds significantly to the information gained during exercise testing.

Aged↗
PubMed1992

Computer probability estimates of angiographic coronary artery disease: transportability and comparison with cardiologists' estimates.

A computer algorithm for estimating probabilities of any significant coronary obstruction and triple vessel/left main obstructions was derived, validated, and compared with the assessments of cardiac clinician angiographers. The algorithm performed at least as well as the clinicians when the latter knew the identity of the patients whose angiograms they had decided to perform. The clinicians were more accurate when they did not know the identity of the subjects but worked from tabulated objective data. Referral and value induced bias may affect physician judgment in assessing disease probability. Application of computer aids or consultation with cardiologists not directly involved with patient management may assist in more rational assessments and decision making.

Adult↗
PubMed1992

The significance of lead strength on ST changes during treadmill stress tests.

The contribution of relative lead strengths to ST depression during exercise was evaluated in 334 patients who had both a treadmill stress test and an angiogram. Patients were referred for exercise testing for the evaluation of suspected or known coronary artery disease. This was accomplished by comparing the magnitude of ST-segment depression to a constructed ST/R ratio. Using a cutoff of 0.1 for the ST/R ratio, the data were compared to the sensitivity and specificity of the 1 mm criteria for ST depression. There was only a slight increase in sensitivity (59% vs 63%) and specificity (60% vs 78%) for the ST/R ratio in comparison to the standard ST depression. However, when these two criteria were reevaluated for patients with less than or equal to 10.0 mm of R wave amplitude, the 0.1 ST/R ratio had a small decrease in specificity (94% vs 80%) when compared to 1 mm of ST depression and a marked increase in sensitivity with 31% for the standard ST depression and 82% using the ST/R ratio. In those with an R wave greater than 20 mm, 1 mm of ST depression was much more sensitive than the ST/HR ratio (95% vs 59%), but the ratio was more specific than the conventional ST depression (78% vs 59%). It is concluded that ST depression should be corrected for R wave amplitude in patients with R waves less than 10 mm and over 20 mm.

Coronary Angiography↗
PubMed1991

Significance of signal-averaged P-wave changes during exercise in patients with coronary artery disease and correlation with angiographic findings.

The maximal P-wave duration in all time-aligned leads, and the maximal P-wave amplitude in leads V5 and V6 were measured on a 12-lead, signal-averaged electrocardiogram during the recovery period of an exercise stress test (EST). The study group consisted of 75 patients with coronary artery disease (CAD) documented by greater than or equal to 50% diameter stenosis in 1 or more arteries and a control group of 47 subjects, 15 of them young volunteers and 32 with no or minimal coronary atherosclerosis and normal left ventricular function. All subjects underwent a symptom limited EST, with use of the Ellestad protocol. Signal-averaged P waves recorded before exercise, and for the first 6 minutes in recovery were measured using a 5x magnifier. The mean P duration before exercise in the control group was 107 +/- 16 ms (+/- 1 standard deviation) and 111 +/- 15 ms at the third minute of recovery, (p less than 0.001). In patients with CAD it was 112 +/- 12 and 129 +/- 19 ms (+/- 1 standard deviation), p less than 0.001, respectively. Differences in P-wave duration were found to be statistically significant (p less than 0.001) throughout recovery in the group with CAD when compared with control and maximal values at the third minute. The increase in P-wave duration (greater than or equal to 20 ms) was used as an additional parameter to exercise-induced ST-segment depression, ST elevation, or anginal pain for the test interpretation. The sensitivity increased from 57 to 75% and the specificity decreased from 85 to 77%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Dacron-woven pacemaker pouch. Influence on long-term pacemaker mobility.

Pacemaker migration can interfere with correct pacing system function and patient comfort. A Dacron pouch has been developed which may prevent these problems. To assess the efficacy of the pouch, we measured various factors of pacemaker mobility in 100 patients after long-term follow-up. The patients were divided into three groups on the basis of their dictated operative reports: group 1, no pouch or anchoring stitch; group 2, pouch only; group 3, anchoring stitch to pacemaker header or pouch. The average age of the study population was 74.3 +/- 11 years. Total follow-up time was 42 +/- 28 months (group I, 53 +/- 32 months; group 2, 36 +/- 23 months; group 3, 34 +/- 25 months). There were no significant differences when pacemakers were measured for movement in the inferosuperior and lateromedial directions, nor was there any difference in the distance between the incision scar and the pacemaker header in any group. There was a significant difference between group 1 and groups 2 and 3 when the degree of tilt of the pacemaker off the chest wall was compared. This was 46 degrees +/- 34 degrees for group 1 and 27 degrees +/- 26 degrees and 26 degrees +/- 27 degrees for groups 2 and 3, respectively (p less than 0.02 for both). These data suggest that the Dacron pouch does not restrict pacemaker mobility parallel to the chest wall during long-term follow-up but does reduce the angle to which the pacemaker can be tilted relative to the chest wall.

Aged↗
PubMed1979

Chronotropic incompetence in exercise testing.

Patients with chronotropic incompetence, defined as a failure of the heart rate response to exercise to rise to within two standard deviations of the expected increase with exercise, where studied and compared to patients with known coronary disease by angiogram with and without ST segment depression. 72% of the patients with chronotropic incompetence but without ST depression had significant coronary heart disease. The demonstration of chronotropic incompetence in exercise testing has important predictive implications and should be looked upon as carefully as ST segment changes. There was no evidence of SA node ischemia in these patients. Intrinsic heart rate measurements done in this study suggest autonomic dysfunction as a possible pathophysiologic mechanism for chronotropic incompetence. The heart rate response to exercise may be a useful predictor of the presence and severity of coronary disease. Therefore, a predicted heart rate response with standard deviation for age and sex should be included as part of the stress test protocol.

Adult↗
PubMed1979

Predicting coronary artery disease with treadmill stress testing: changes in R-wave amplitude compared with ST segment depression.

Coronary angiograms and treadmill stress tests were reviewed independently in 108 nonconsecutively selected cases. There were 16 patients (15%) with infarcts on ECG. Changes in R-wave amplitude and ST segments during exercise were evaluated to determine the sensitivity and specificity of each as a predictor of coronary artery disease (CAD). ST segment changes had a sensitivity of 49%, and a specificity of 74%. The sensitivity increased to 55% when infarcts were excluded. R-wave amplitude changes had a sensitivity of 68% and a specificity of 84%. The sensitivity increased to 78% when infarcts were excluded. An index formed by the sum of the change in R-wave amplitude and the magnitude of ST segment change yielded a sensitivity of 76% and specificity of 78%. The sensitivity increased to 84% when infarcts were excluded. There was no statistical difference between specificities for each criteria. Of those patients with an R-wave amplitude decrease, 69% had no coronary artery atherosclerosis, while 31% had significant lesions. Of those patients with no change or an increase in R-wave amplitude, 83% had coronary artery atherosclerosis, while 17% were normal. Of the 83% with coronary artery atherosclerosis, 81% had two and three vessel disease, while only 19% had single vessel disease. No change or an increase in R-wave amplitude during treadmill stress testing is a more reliable indicator of CAD in our laboratory than ST segment changes.

Adult↗
PubMed1979

Cardiac dysfunction in a patient with familial hypokalemic periodic paralysis.

A 19-year-old white man with familial hypokalemic periodic paralysis developed evidence of cardiac dysfunction during a episode of flaccid paralysis. This consisted of elevated total creatine phosphokinase (CPK), an increased myocardial fraction of CPK (myocardial band), alteration in the lactic dehydrogenase isoenzyme pattern, severe bradycardia, and evidence of left ventricular dysfunction. These findings, in conjunction with selected cases from the literature, suggest the possibility that cardiomyopathy may be a heretofore unrecognized complication of this disorder.

Adult↗
PubMed1978

Significance of changes in R wave amplitude during treadmill stress testing: angiographic correlation.

Coronary angiograms and treadmill stress tests were reviewed in 89 patients. Changes in R wave amplitude were measured in the control and immediate postexercise periods. Of 45 patients with normal coronary arteries, 41 (91 percent) had a decrease in R wave amplitude (P less than 0.01); 3 (7 percent) had an increase in amplitude, including 2 with abnormal left ventriculograms. The remaining patient (2 percent) had abnormal wall motion but no change in R wave amplitude. Among the 44 patients with significant coronary artery disease (70 percent or greater luminal narrowing in one or more vessels), R wave amplitude increased after exercise in 26 (59 percent) with more severe coronary artery disease. R wave amplitude decreased in 18 patients (41 percent) with normal or minimally abnormal resting ventriculograms and less severe coronary artery disease (P less than 0.01). Changes in R wave amplitude reflect ventricular function, an increase in R wave amplitude reflecting more severe dysfunction and severe coronary narrowing. A decreased R wave amplitude indicates normal or minimal dysfunction and is strongly associated with normal coronary angiograms.

Adult↗
PubMed1978

Significance of chest pain during treadmill exercise: correlation with coronary events.

A follow-up study of 1,402 patients with a positive maximal treadmill stress test was made to evaluate the significance of angina during the test. Life tables were constructed and evaluated for significance of age, sex and work load at onset of angina. Coronary events (myocardial infarction, progression of angina and coronary death) were twice as frequent in subjects with angina and S-T segment depression as in those without angina. The increased incidence in 4 years held for all coronary events and was still doubled at 7 years for progression of angina and coronary death. The incidence of coronary events was more than twice as great when the angina was induced by a light work load (4 metabolic equivalents = METS) as when it was induced by a heavy work load (8 to 9 METS). Men aged 41 to 50 years having angina during exercise testing had a 3-fold greater incidence of coronary events and a 4-fold greater incidence of myocardial infarction compared with their counterparts who had S-T segment depression alone. In this study, angina during exercise testing identified 85% of true positive tests for coronary artery disease, whereas S-T depression alone identified only 64% of such tests. Thus, angina during exercise testing increases the sensitivity of the test and identifies cohorts of subjects at high risk for subsequent coronary events.

Age Factors↗
PubMed1978

Comparison of S-T segment changes on exercise testing with angiographic findings in patients with prior myocardial infarction.

Ninety-seven patients with a prior transmural myocardial infarction who underwent coronary angiography and treadmill stress testing were studied retrospectively to assess the reliability of the exercise electrocardiogram in detecting additional disease in patients with a prior infarction. In patients with a previous inferior wall infarction, the S-T response to the treadmill stress test had a high degree of sensitivity (87 percent) and specificity (90 percent) in detecting additional significant coronary artery disease. However, in patients with a previous anteroseptal wall infarction, the S-T response had much less sensitivity (52 percent), but the degree of specificity remained high (90 percent). In this group a positive test suggested the presence of ischemia in the lateral or inferoposterior region of the myocardium, or both. A negative S-T response was of little value in distinguishing among groups of patients with single or multiple vessel coronary artery disease. The presence of an anterior ventricular aneurysm is most likely responsible for this low sensitivity rate because it generates an opposing force to the ischemic vector, thereby cancelling the S-T segment changes and producing a false negative treadmill stress test. The resting surface electrocardiogram proved useful in predicting a false negative exercise test. The presence of Q waves in the precordial leads extending to lead V4 or beyond decreased the sensitivity rate of treadmill stress testing to 33 percent.

Adult↗
PubMed1978

Coronary sinus pacing clinical follow-up.

Coronary sinus pacing is a safe and effective means of pacing from the atrium. In 66 patients with an average follow-up of 14 months, there was a 14% failure rate. There were transient problems in 14% which were subsequently corrected. There was a 6% death rate which was not pacemaker related. Successful atrial pacing with thresholds up to 6.0 mA is feasible. Atrial pacing was successful in 18 of 19 patients with varying degrees of atrioventricular block. Our experience with a new electrode has been very satisfactory.

Aged↗
PubMed1978

Evaluation of R wave amplitude changes versus ST-segment depression in stress testing.

Exercise ECGs and coronary angiograms were reviewed in 266 patients (81 normals and 185 with significant coronary artery disease). Thirty-three false positive and 96 false negative ST responses to stress testing were purposely chosen to determine if the R wave could reduce the number of false ST responses. R wave amplitude changes were measured in the control and in the immediate postexercise period. An increase or no change in R wave was taken as evidence of an abnormal response, while a decrease in the R wave was a normal response. The sensitivity by ST segment was 48% and the specificity was 59%. These values were low because of the large number of false positive and negative ST responses in the study. It was our purpose to determine if these lowered values could be significantly improved by the R wave. Using R wave criteria, the sensitivity was 63% (P is less than 0.01) while the specificity was 79% (P is less than 0.01). The sensitivity and specificity of stress testing can be significantly improved using R wave changes.

Coronary Angiography↗