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Biomedical subjects

R J Krone

Publications and source records attributed to R J Krone.

At least 37 records · Page 2Linked to original sources
PubMed1993

Detection and significance of myocardial ischemia in stable patients after recovery from an acute coronary event. Multicenter Myocardial Ischemia Research Group.

OBJECTIVE: To determine the clinical significance of silent and symptomatic myocardial ischemia detected by noninvasive testing in stable postcoronary patients. DESIGN: Cohort study with a mean 23-month follow-up. SETTING: Ambulatory outpatients after recent hospitalization for an acute coronary event. PATIENTS: Nine hundred thirty-six patients (76% male; mean age, 58 years) who were clinically stable 1 to 6 months after hospitalization for acute myocardial infarction or unstable angina. INTERVENTIONS: Noninvasive testing involved rest, ambulatory, and exercise electrocardiograms and stress thallium-201 scintigraphy. MAIN OUTCOME MEASURES: Cox regression analysis was used to evaluate the risk (hazard ratio) of first recurrent primary events (cardiac death, nonfatal infarction, or unstable angina) or restricted events (cardiac death or nonfatal infarction) associated with ischemic noninvasive test results. RESULTS: ST segment depression on the rest electrocardiogram was the only noninvasive test variable that identified a significantly increased risk (P = .05) for first recurrent primary events (hazard ratio; 95% confidence limits): rest electrocardiogram ST depression (1.5; 1.00, 2.25); ambulatory electrocardiogram ST depression (0.86; 0.49, 1.51); exercise electrocardiogram ST depression (1.13; 0.82, 1.56); and stress thallium-201 reversible defects (1.3; 0.96, 1.74). Test results were similar for first recurrent restricted events, and in patients with and without angina. Significantly increased risk (P < .05) was noted when exercise-induced ST depression occurred in patients who also had reduced exercise duration (hazard ratio, 3.4) or when reversible thallium-201 defects occurred in patients who also had increased lung uptake (hazard ratio, 2.8). Each high-risk subset made up less than 3% of the population and contained less than 6% of patients with first primary events. CONCLUSION: Detection of silent or symptomatic myocardial ischemia by non-invasive testing in stable patients 1 to 6 months after an acute coronary event is not useful in identifying patients at increased risk for subsequent coronary events.

Adult↗
PubMed1993

Long-term prognostic significance of ST segment depression during acute myocardial infarction. The Multicenter Diltiazem Postinfarction Trial Research Group.

OBJECTIVES: The purpose of this study was to evaluate the long-term prognostic value of ST segment depression on the electrocardiogram (ECG) in patients with acute myocardial infarction. BACKGROUND: The prognostic importance of ST segment depression on the ECG has been studied in small groups of patients with infarction, but larger numbers are needed. METHODS: Coronary care unit ECGs of 1,234 patients who survived the coronary care unit with acute Q wave (n = 896) or non-Q wave (n = 338) myocardial infarction were analyzed for the presence of ST segment depression. Patients were followed up for up to 4 years. RESULTS: ST segment depression was present in 607 patients. Those with ST segment depression had a 1-year mortality rate of 10.3% compared with a rate of 5.6% for those without ST segment depression (p = 0.002). This effect was seen in both the Q wave and non-Q wave subgroups. Of the 437 patients with anterior ST segment elevation, those with ST segment depression in other regions had a 13.6% 1-year mortality rate compared with a rate of 6.9% for those with no ST segment depression (p = 0.0005). Of the 514 patients with inferior ST segment elevation, those with ST segment depression in other leads had an 11.0% 1-year mortality rate compared with a 1.8% rate for those with no ST segment depression (p = 0.0001). The Cox proportional hazards model showed that ST segment depression was an independent predictor of mortality over the follow-up period. CONCLUSIONS: ST segment depression on the admitting ECG in patients with acute myocardial infarction is a predictor of increased mortality in the year after infarction.

Adult↗
PubMed1992

The role of risk stratification in the early management of a myocardial infarction.

OBJECTIVE: To review the literature on early management of myocardial infarction. DATA SOURCES: Papers published or referenced in major English-language cardiology journals for the last 15 years. STUDY SELECTION: Large recent multicenter studies and the guidelines for early management of patients with acute myocardial infarction (American College of Cardiology/American Heart Association Task Force) were emphasized. DATA SYNTHESIS: A strategy for risk stratification was developed from information available in the emergency department, from the first days of the hospitalization, and before discharge to identify patients in whom intervention might improve prognosis. CONCLUSIONS: Treatment of myocardial infarction requires establishing patency of the infarct-related artery, usually with thrombolysis. Risk stratification begins in the emergency department (phase 1) using clinical (primarily the electrocardiogram) and historical data to identify patients at risk for massive infarction. For patients at highest risk, the efficacy of thrombolytic therapy must be assured and, if not effective, emergency angiography and mechanical reperfusion should be considered. During days 2 to 5, (phase 2), patients with large amounts of ischemic myocardium, postinfarction angina, "flash" pulmonary edema, or anterior non-Q infarctions are identified and studied. Predischarge (phase 3) stratification identifies those patients at risk for early death. A previous infarction, an ejection fraction less than 0.40, pulmonary congestion during the hospitalization, delayed afterpotentials on signal-averaged electrocardiography, symptomatic ventricular ectopic beats, decreased heart rate variability, limited exercise tolerance, or ischemia on exercise testing identifies patients at high risk. Patients with jeopardized myocardium must be identified for revascularization to try to improve survival. More data are needed to determine whether angioplasty or bypass surgery will improve prognosis in these patients.

Algorithms↗
PubMed1991

Electrocardiographic subset analysis of diltiazem administration on long-term outcome after acute myocardial infarction. The Multicenter Diltiazem Post-Infarction Trial Research Group.

The effect of diltiazem on long-term outcome after acute myocardial infarction (AMI) was assessed in 2,377 patients enrolled in the Multicenter Diltiazem Post-Infarction Trial and subsequently followed for 25 +/- 8 months. The study population included 855 patients (36%) with at least 1 prior AMI before the index infarction and 1,522 patients (64%) with a first AMI, of whom 409 (27%) had a first non-Q-wave AMI, 664 (44%) a first inferior Q-wave AMI, and 449 (30%) a first anterior Q-wave AMI. This post hoc analysis revealed that, among patients with first non-Q-wave and first inferior Q-wave AMI, there were fewer cardiac events during follow-up in the diltiazem than in the placebo group, and that the reverse was true for patients with first anterior Q-wave AMI or prior infarction. The diltiazem:placebo Cox hazard ratio (95% confidence limits) for the trial primary end point (cardiac death or nonfatal reinfarction, whichever occurred first) was: first non-Q-wave AMI-0.48 (0.26, 0.89); first inferior Q-wave AMI-0.66 (0.40, 1.09); first anterior Q-wave AMI-0.82 (0.51, 1.31); and prior AMI-1.11 (0.85, 1.44). Use of cardiac death alone as an end point gave an even more sharply focused treatment difference: first non-Q-wave AMI-0.46 (0.18, 1.21); first inferior Q-wave AMI-0.53 (0.27, 1.06); first anterior Q-wave AMI-1.28 (0.68, 2.40); prior infarction-1.26 (0.90, 1.77). Further analysis revealed that these differences in the effect of diltiazem in large part reflected the different status of the 4 electrocardiographically defined subsets in terms of left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Diltiazem↗
PubMed1991

PTCA update: is your patient now a candidate? Even complex multivessel lesions may succumb to balloon dilation.

Indications for PTCA continue to grow. In complex multivessel lesions, PTCA now has high primary success and low complication rates. Dilation of chronic total occlusions is less successful than in subtotal occlusions but may relieve angina in some patients. Occluded saphenous vein grafts can be dilated and long-term patency achieved--particularly in grafts implanted for less than 36 months. Restenosis remains a major drawback; antithrombotic therapy (with heparin during PTCA and aspirin thereafter) is recommended. PTCA is a useful adjunct in acute myocardial infarction when thrombolytic therapy fails or is contraindicated, or when significant luminal narrowing remains after thrombolysis. Investigational devices--atherectomy catheters, lasers or laser balloons, and intracoronary stents--may further expand the role of PTCA.

Angioplasty, Balloon, Coronary↗
PubMed1990

The independence of cycle length variability and exercise testing on predicting mortality of patients surviving acute myocardial infarction. The Multicenter Postinfarction Research Group.

Cycle length variability (CLV), defined as the standard deviation of normal cycle length intervals, has been found to be a powerful predictor of subsequent mortality in a population of 808 survivors of acute myocardial infarction. Decreased CLV is associated with a significant increase in mortality. CLV remained an independent predictor of outcome even after adjusting for left ventricular ejection fraction, clinical risk factors, heart rate and ventricular arrhythmias. In the same population of survivors of acute myocardial infarction, the results of exercise testing also strongly predicted outcome, with those failing to take the test having the worst survival, and those completing the low-level stress test taken before discharge having the best prognosis. The hypothesis that the status of stress test (completed; did not complete; failed to take) and CLV were measuring the same factor related to mortality was tested. Although the distribution of CLV was shifted to higher CLV in patients who completed the test and to lower CLV in those who failed to take the test, both predictors of mortality remained independent predictors of long-term mortality (average of 31 months of follow-up) after controlling for each other. Moreover, subgroups with an approximate 15-fold difference in mortality were defined using both variables (CLV less than 50 ms, did not take test had a 54% mortality; CLV greater than 100 ms, completed the test had a mortality of 3.5%). CLV is a measure of autonomic tone; it is not strongly related to exercise ability and using the results of both stress testing and CLV results in the identification of subgroups of postinfarction patients with markedly disparate risks of mortality.

Blood Pressure↗
PubMed1989

Risk stratification in patients with first non-Q wave infarction: limited value of the early low level exercise test after uncomplicated infarcts. The Multicenter Post-Infarction Research Group.

Risk stratification using clinical and historical variables plus early low level exercise testing was performed in 141 patients with a first non-Q wave myocardial infarction. The 111 patients who performed the exercise test had a 3.6% cardiac mortality rate in the first year compared with 13.3% in the 30 patients who could not exercise (p = 0.063), and a 1 year incidence rate of recurrent cardiac events (cardiac death or recurrent nonfatal myocardial infarction) of 10.8% compared with 23.3% (p = 0.127). Patients who developed ischemia (ST depression or angina) during the test had an increased incidence of cardiac events in the year after the infarction (odds ratio greater than 3, p less than 0.05). When patients were subgrouped by the presence or absence of pulmonary congestion, the discriminatory value of the exercise test was seen to reside primarily in the cohort with pulmonary congestion. For example, ST depression during exercise in this group identified patients with a 71% incidence of cardiac events in the year after the infarction compared with 5.3% for those without ST depression (odds ratio 45, p = 0.002). In the patients without pulmonary congestion, the exercise test had no discriminatory value. It is concluded that early low level exercise testing has a limited role after an uncomplicated non-Q wave infarction, but is useful in patients with clinical markers of higher risk.

Electrocardiography↗
PubMed1987

Usefulness of low-level exercise testing early after acute myocardial infarction in patients taking beta-blocking agents.

The value of low-level exercise testing early after acute myocardial infarction (AMI) in 207 patients taking beta-blocking drugs was evaluated in a multicenter study of prognosis after AMI. After stratifying patients according to the absence of significant rales upon admission or pulmonary congestion on the admitting chest x-ray, the results of the exercise test (ability to complete the 9-minute protocol) permitted a large cohort (108 patients, 52% of exercising patients) with no deaths from cardiac causes in the year after AMI to be identified. The results suggest that even in patients taking beta-blocking agents, low-level exercise testing together with clinical stratification has value in identifying a large group of patients with a good prognosis after AMI.

Adrenergic beta-Antagonists↗
PubMed1987

Long-term outcome of revascularization of the anterior coronary arteries with crossed double internal mammary versus saphenous vein grafts.

When simultaneous revascularization of the left anterior descending (LAD) artery and the proximal segments of the diagonal LAD and marginal coronary arteries is required, the direction and location of these vessels allow excellent alignment of the left internal mammary artery (IMA) with the LAD and the right IMA with the diagonal LAD or marginal arteries, an approach originally described in 1976. To analyze and compare the long-term outcome of this approach versus the saphenous vein bypass graft (SVG) approach for anterior coronary revascularization, we reviewed 43 patients who had these crossed double IMAs (CDIMAs) and 53 patients who had SVGs to the same obstructed anterior coronary arteries during 1973 to 1978; 32 patients in the CDIMA group and 43 in the SVG group also had SVGs to other diseased vessels. The two groups had similar demographic and epidemiologic characteristics. The linearized incidence of late cardiac death, reoperation, recurrent angina, and infarction was 0.2%, 0.7%, 1.4%, and 0% per patient-year, respectively, in the CDIMA group, and 1.6%, 2.4%, 7.8%, and 1.8% per patient-year in the SVG group (p less than 0.01 for each event). At 5 years, the actuarial number of patients with CDIMAs free of late cardiac death was 100%, of reoperation 98%, of recurrent angina 98% (p less than 0.01), and infarction 100% (p less than 0.01), versus 94%, 98%, 84%, and 94%, respectively, in the SVG group. At 10 years, the actuarial incidence of all events was substantially and significantly less in patients with CDIMAs. CDIMAs have significantly better prognostic effects than SVGs when revascularization of the anterior coronary arteries is required. This is currently our preferred approach in these selected patients.

Actuarial Analysis↗
PubMed1986

Successful percutaneous removal of retained broken coronary angioplasty guidewire.

The use of a pigtail left ventriculography catheter to retrieve a coronary angioplasty guidewire that had become entrapped in a small coronary artery and broken off with the proximal end in the descending thoracic aorta is reported. A pigtail catheter was advanced to the ascending aorta and twirled, winding the wire around it, removing the wire from the small artery.

Angioplasty, Balloon↗
PubMed1985

Low-level exercise testing after myocardial infarction: usefulness in enhancing clinical risk stratification.

Of 866 patients enrolled in our multicenter study, 667 performed a low-level exercise test early after myocardial infarction, most before discharge. Excluding seven patients who died before the test could be considered, there was a 14% 1 year cardiac mortality in 192 patients who did not take the test (150 for medical and 42 for logistic reasons) compared with 5% in those who did (p less than .0001). Of those who took the test, 12% subsequently underwent bypass grafts surgery compared with 14% of those who did not (p greater than .05). Decreased mortality in the year after the infarction in those taking the test was associated with an increase in blood pressure to 110 mm Hg or higher (3% vs 18%; p less than .001), ability to complete the 9 min test (3% vs 8%; p less than .01), and the absence of couplets (4% vs 13%; p less than .05) or any ventricular ectopic depolarizations (4% vs 7%, p less than .05) before, during, or after exercise. Achievement of a blood pressure of 110 mm Hg or higher during exercise in patients with no evidence of pulmonary congestion on the chest x-ray identified a group of 454 patients (70% of those taking the test) with a 1 year cardiac mortality of 1% compared with 13% in the remaining patients (p less than .0001). Logistic models showed that the exercise test contributed independent prognostic information for cardiac death, new infarction, and bypass surgery. Results of low-level exercise testing before hospital discharge combined with clinical features of the infarction can effectively identify patients at low risk for subsequent cardiac mortality.

Angina Pectoris↗
PubMed1983

Noninvasive ergonovine maleate provocative testing for coronary artery spasm: the need for routine thallium-201 imaging.

We administered ergonovine and used both electrocardiographic monitoring and thallium-201 [201Tl] imaging to detect reversible ischemia in 100 patients. Patients already established as having coronary artery spasm and those with nonbypassed, proximal, high-grade coronary artery stenosis were excluded. No complication occurred in any patient. The use of thallium imaging in addition to electrocardiographic monitoring resulted in a higher degree of sensitivity than did ECG monitoring alone. Fourteen patients demonstrated evidence of coronary artery spasm as documented by 201Tl imaging but of the 14, significant ECG changes occurred in only 50%, and classic ST segment elevation in 21%. Thus, in carefully selected patients the noninvasive provocation of coronary spasm can be accomplished safely, but ECG monitoring must be combined with thallium-201 imaging to achieve an acceptable degree of sensitivity.

Adult↗
PubMed1983

Long-term prognosis after first Q-wave (transmural) or non-Q-wave (nontransmural) myocardial infarction: analysis of 593 patients.

Follow-up results in 593 patients less than or equal to 7 years (mean 4.7) after hospital discharge for their first myocardial infarction (MI) are presented. Patients were grouped according to the presence or absence of Q waves on electrocardiograms after the MI and by peak serum glutamic oxalacetic transaminase (SGOT) level during hospitalization. Cardiac mortality varied. Patients with Q-wave infarcts and an SGOT level less than or equal to 240 IU/liter had a cardiac mortality of 3.1% per year, whereas patients with Q-wave MI and an SGOT level greater than 240 IU/liter had an 11% 6-month mortality and a 3.8% per year cardiac mortality thereafter. However, patients with non-Q-wave (nontransmural) MI had a excellent survival rate for 2 years (96.8%) which continued in patients aged less than or equal to 60 years thereafter. However, patients with non-Q-wave infarcts aged greater than 60 years had a 12% per year cardiac mortality in the third post-MI year and an additional 12% died each year thereafter. Early mortality was related to enzyme level, whereas late mortality was a function of type (Q-wave or non-Q-wave) and age.

Aged↗