Inferior myocardial infarction. High-risk subgroups

Pathophysiology and management of right heart ischemia

Acute right coronary artery occlusion proximal to the right ventricular (RV) branches results in right ventricular free wall dysfunction, exerting mechanically disadvantageous effects on biventricular performance. Depressed RV systolic function decreases transpulmonary delivery of left ventricular (LV) preload, resulting in diminished cardiac output. The ischemic right ventricle is stiff, dilated, and volume dependent, resulting in pandiastolic RV dysfunction and septally mediated alterations in LV compliance, which are exacerbated by elevated intrapericardial pressure. Under these conditions, RV pressure generation and output are dependent on LV-septal contractile contributions, governed by both primary septal contraction and paradoxical septal motion. When the culprit coronary lesion is distal to the right atrial (RA) branches, augmented RA contractility enhances RV performance and optimizes cardiac output. Conversely, more proximal occlusions result in ischemic depression of RA contractility, which impairs RV filling and performance, resulting in more severe hemodynamic compromise. Bradyarrhythmias limit output generated by the rate-dependent noncompliant ventricles. Hemodynamic compromise may respond to volume resuscitation and restoration of physiologic rhythm. Vasodilators and diuretics should generally be avoided. In some patients, parenteral inotropic stimulation may be required. The right ventricle appears to be relatively resistant to infarction and recovers even after prolonged occlusion. The term RV "infarction" appears to be somewhat of a misnomer, for in most patients acute RV dysfunction represents ischemic but predominantly viable myocardium. Although RV performance improves spontaneously even in the absence of reperfusion, recovery of function may be slow and associated with high in-hospital mortality. Reperfusion enhances recovery of RV performance and improves the clinical course and survival.

Comparison of right ventricular volume measurement between segmented k-space gradient-echo and steady-state free precession magnetic resonance imaging

PURPOSE

To compare right ventricular volume measurements and their reproducibility between steady-state free precession (SSFP) and conventional turbo gradient-echo (TGE) imaging.

MATERIALS AND METHODS

Right ventricular volumes and observer variabilities were compared between SSFP and TGE in 31 subjects (21 normal volunteers and 10 subjects with heart failure). For further internal validation of the right ventricular volumes, the left ventricle (LV) and right ventricle (RV) stroke volumes were compared for the normal volunteers.

RESULTS

The volumes as measured by SSFP were significantly larger than for TGE (mean bias end-diastolic volume [EDV] 11.1 +/- 14.2, end-systolic volume [ESV] 9.8 +/- 9.75). SSFP had lower interobserver variability (SSFP EDV -10.1 +/- 11.6 vs. TGE EDV -6.2 +/- 18.5) and intra-observer variability (SSFP EDV -2.0 +/- 6.3 vs. TGE EDV -6.1 +/- 14.8). The mean absolute differences between LV and RV stroke volumes for 21 normal volunteers were: TGE 5.8 +/- 12.9 (r(2) = 0.72), SSFP 4.6 +/- 6.9 (r(2) = 0.92).

CONCLUSION

SSFP and TGE yield different measurement values of RV volumes with SSFP, providing a more reproducible measurement.

ECG discrimination between right and left circumflex coronary arterial occlusion in patients with acute inferior myocardial infarction: value of old criteria and use of lead aVR

STUDY OBJECTIVES

Prior studies have proposed several ECG criteria for identifying the culprit artery in patients with acute inferior myocardial infarction (MI). We applied each criterion to our patients to assess its utility. In doing so, we discovered a previously unreported, but highly useful, criterion utilizing lead aVR.

STUDY DESIGN

Retrospective review.

PATIENTS

Thirty consecutive patients with symptoms of acute MI, ST-segment elevation in the inferior ECG leads, an appropriate rise and fall of creatine kinase and troponin I levels, and coronary arteriography within 7 days of the onset of symptoms.

MEASUREMENTS

The ECG recorded within 24 h of the onset of symptoms that had the most prominent ST-segment changes was analyzed. In the 12 standard leads and in lead V(4)R, ST-segment elevation or depression was measured 0.06 s after the J point.

RESULTS

Four previously described criteria were useful in identifying the right coronary artery (RCA) or the left circumflex coronary artery (LCX) as the culprit: ST-segment elevation in lead I, ST-segment more or less elevated in lead II than in lead III, ST-segment elevation >or= 0.5 mm in lead V(4)R, and various combinations of ST-segment elevation or depression in leads V(1) and V(2). A new criterion was found to be at least as useful as any previously described: the presence and amount of ST-segment depression in lead aVR.

CONCLUSIONS

At least five different ST-segment criteria help to identify the RCA or the LCX as the culprit artery in patients with acute inferior MI. One of these, the amount of ST-segment depression in lead aVR, has not been reported previously and needs validation in a larger study.

A novel rabbit model of variably compensated complete heart block

Complete heart block (CHB) provides a useful substrate for study of bradycardia-dependent ventricular arrhythmias and cardiac function. Existing CHB animal models are limited by surgical recovery time and reliance on intrinsic escape rhythms. We describe a novel closed-chest rabbit model of CHB involving transcatheter radiofrequency (RF) atrioventricular (AV) node ablation and ventricular rate control with chronic transvenous pacing. Permanent CHB was achieved in 34 of 38 attempts overall. Procedural mortality due to cardiac tamponade (n = 2), airway complications (n = 2), and unknown causes (n = 5) occurred in nine animals. Survivors with CHB (n = 28) were maintained for < or = 22 days, during which there were three late deaths related to infection (n = 1) or respiratory distress (n = 2). None of the survivors with CHB showed recovery of AV conduction or pacemaker capture loss during chronic ventricular pacing at about one-half normal sinus rates, and 25 animals surviving to death showed no overt signs of hemodynamic compromise such as lethargy, poor feeding, or respiratory distress. This approach provides a reproducible nonsurgical CHB model with adjustable ventricular rate control.

Dominant right ventricular infarction: is angioplasty the optimal therapeutic approach?

Approximately 30% of all acute inferior myocardial infarctions (AIMI) are accompanied by acute right ventricular infarction (ARVI) as a consequence of proximal right coronary artery (RCA) occlusion. Fifty per cent of all patients with ARVI manifest hypotension, jugular venous distension, and dyspnoea with clear lung fields, which is then considered as dominant acute RVI (ARVI). The in hospital mortality rate of patients with ARVI who are treated traditionally is very high. Thrombolytic therapy is relatively ineffective, while primary angioplasty is a more recent approach yet to be established as optimal treatment for patients with ARVI. Thirty-eight patients with dominant ARVI were admitted to our CCU over a period of 24 months. The patients were retrospectively divided into 3 groups according to treatment: Group I (n = 16): traditional treatment; Group II (n = 12): thrombolytic therapy (streptokinase); Group III (n = 10): angioplasty after urgent coronarography. We tested the difference in the number of deaths in all groups by the Fisher exact test. There was a significant difference in the number of deaths between Group I and Group III (P < 0.05). Mortality reduction was also noted between Group II and Group III, which, however, proved to be statistically insignificant.

Clinical significance of ST-segment elevation in lead V1 in patients with acute inferior wall Q-wave myocardial infarction

BACKGROUND

This study was designed to determine the clinical significance of ST-segment elevation in the precordial leads (leads V1 and V2) in acute Q-wave inferior wall myocardial infarction.

METHODS AND RESULTS

One hundred fifty-eight consecutive patients with acute Q-wave inferior wall myocardial infarction were classified into 3 groups on the basis of the initial ST-change in V1 (group 1 = 29 patients with ST elevation, group 2 = 97 patients with ST depression, and group 3 = 32 patients with no ST-segment change). The right coronary artery was the infarct-related artery in all the patients in group 1. Although there was no significant difference between groups 1 and 2, the number of left ventricular asynergic segments was larger and the incidence of major in-hospital arrhythmias was higher in groups 1 and 2 compared with group 3. Patients in group 1 had a significantly higher incidence of proximal lesion (86%) and right ventricular infarction (69%) than the other 2 groups did. When ST elevation in leads V1 and V2 was considered, 14 of 15 patients (93%) with ST elevation only in V1 had right ventricular infarction, whereas 6 of 14 patients (43%) with ST elevation in both V1 and V2 had right ventricular infarction (P =.011).

CONCLUSIONS

ST-segment elevation in V1 on admission in patients with acute Q-wave inferior wall myocardial infarction indicates a right coronary artery lesion associated with a larger infarct size and a higher incidence of major in-hospital arrhythmias.

Value of ST elevation in lead III greater than lead II in inferior wall acute myocardial infarction for predicting in-hospital mortality and diagnosing right ventricular infarction

ST elevation in lead III > II has a higher sensitivity than lead V4R in diagnosing right ventricular myocardial infarction. Lead III > II is also predictive of in-hospital mortality.

Acute myocardial infarction complicated by heart block in the elderly: prevalence and outcomes

BACKGROUND

Although second- and third-degree heart block (HB) are common conduction disorders associated with acute myocardial infarction (MI), patient characteristics and HBs association with outcomes, particularly among the elderly, remain poorly defined.

METHODS

We evaluated 106,780 Medicare beneficiaries aged 65 years and older treated for acute MI between January 1994 and February 1996 for development of HB. HB and non-HB patients were compared by univariate analysis, and the influence of HB on outcomes was evaluated by unadjusted and multiple logistic regression.

RESULTS

HB was documented in 5048 (4.7%) patients; 1646 presented with HB and 3402 developed HB during hospitalization. HB was more common among patients with inferior infarctions than anterior infarctions (7.3% vs 3.0%, P =.001), particularly the cohort of patients with inferior MI treated with reperfusion therapy (8.3%). HB patients had higher rates of in-hospital mortality (29.6% vs. 17.5% vs. non-HB patients, P =.001). After adjustment for demographic and clinical factors, HB remained an independent predictor of in-hospital mortality (relative risk [RR] 1.41, 95% confidence interval [CI] 1. 34-1.48), but HB had no prognostic significance at 1 year among hospital survivors (RR 0.94, 95% CI 0.88-1.01). Mortality risks varied on the basis of MI location. Both anterior MI (RR 1.46, 95% CI 1.30-1.63) and inferior MI (RR 1.52, 95% CI 1.39-1.66) patients with HB had increased risks of in-hospital mortality. There was a trend toward increased mortality among patients with anterior MI (RR 1.15, 95% CI 0.99-1.32) at 1 year, whereas those with inferior MI were at lower risk (RR 0.83, 95% CI 0.75-0.98).

CONCLUSIONS

HB is a common complication of acute MI in elderly patients, particularly among patients with inferior MIs who received reperfusion therapy. HB is independently associated with short-term but not long-term mortality.

Impact of right ventricular involvement on mortality and morbidity in patients with inferior myocardial infarction

OBJECTIVES

We sought to evaluate the prognostic impact of right ventricular (RV) myocardial involvement in patients with inferior myocardial infarction (MI).

BACKGROUND

There is uncertainty regarding the risk of major complications in patients with inferior MI complicated by RV myocardial involvement. Whether these complications are related to RV myocardial involvement itself or simply to the extent of infarction involving the left ventricle (LV) is also unknown.

METHODS

We examined the incidence of death and mechanical and electrical complications in patients with (n = 491) and without (n = 638) RV myocardial involvement and in patients with anterior MI (n = 971) in an analysis from the Collaborative Organization for RheothRx Evaluation (CORE) trial. Left ventricular infarct size was assessed by technetium-99m-sestamibi single-photon emission computed tomography and peak creatine kinase, and LV function was assessed by radionuclide angiography. We also performed a meta-analysis in which we pooled the results of our study with previous smaller studies addressing the same question.

RESULTS

Six-month mortality was 7.8% in inferior MI compared with 13.2% in anterior MI. Among patients with inferior MI, serious arrhythmias were significantly more common in patients with RV myocardial involvement who also had a trend toward higher mortality, pump failure and mechanical complications. However, this was not associated with a difference in LV infarct size or function. A meta-analysis of six studies (n = 1,198) confirmed that RV myocardial involvement was associated with an increased risk of death (odds ratio [OR] 3.2, 95% confidence interval [CI] 2.4 to 4.1), shock (OR 3.2, 95% CI 2.4 to 3.5), ventricular tachycardia or fibrillation (OR 2.7, 95% CI 2.1 to 3.5) and atrioventricular block (OR 3.4, 95% CI 2.7 to 4.2).

CONCLUSIONS

Patients with inferior MI who also have RV myocardial involvement are at increased risk of death, shock and arrhythmias. This increased risk is related to the presence of RV myocardial involvement itself rather than the extent of LV myocardial damage.

Right ventricular dysfunction after thrombolysis in patients with right ventricular infarction

BACKGROUND

Right ventricular (RV) infarction is frequently associated with highest risk of death and major complications. Doppler echocardiography can be useful in the diagnosis of RV involvement. The goal of this study was to evaluate Doppler echocardiography features associated with RV involvement and a poor prognosis.

METHODS

Two-dimensional Doppler echocardiography was performed before and after thrombolysis in 108 consecutive patients with an RV infarction. The bedside examination was performed before and 2 to 3 hours after thrombolytic therapy, and repeated after 1 and 7 days. All patients underwent coronary angiography after 20 days, and the perfusion of the coronary-related artery (> thrombolysis in myocardial infarction [TIMI] 3 grade) was evaluated.

RESULTS

Patients were divided into 2 groups according to the recovery of global and regional RV function after thrombolytic therapy. In the group of patients who showed a normalization or improvement of RV wall motion (as assessed by RV wall motion score index), we found a TIMI grade III perfusion in 78% of patients. The analysis of interatrial septal motion and interventricular septal motion showed a normalization in all reperfused patients. Major complication and deaths were more frequent in patients with echocardiographic findings of RV dysfunction persisting after thrombolytic therapy.

CONCLUSION

In patients with RV infarction treated with thrombolysis, persistent RV dysfunction is associated with a higher risk for the development of major cardiac complications and death.

Right ventricular function in patients after acute myocardial infarction assessed with phase contrast MR velocity mapping encoded in three directions

The purpose of the study was to assess global and regional myocardial function of the right ventricle (RV) with the use of phase contrast (PC) velocity mapping in patients after acute myocardial infarction. We examined 8 patients after acute myocardial wall infarction and 10 healthy volunteers for comparison. PC velocity mapping was performed in a single midventricular short-axis slice with velocity encoding in three different directions. RV displacement during systole in the through-plane direction differed significantly between patients and volunteers (P = 0.009). RV myocardial velocity in the through-plane and radial directions, evaluated at time of peak ejection rate, was significantly lower in patients than in healthy volunteers (P<0.05). RV abnormalities may be detected in patients after acute myocardial infarction using PC velocity mapping with velocity encoding in three different directions. Owing to their short acquisition times and relatively easy postprocessing, PC techniques are time-efficient and promising tools for the evaluation of RV function.

Prognostic significance of persistent right ventricular dysfunction as assessed by radionuclide angiocardiography in patients with inferior wall acute myocardial infarction

We evaluated cardiac hemodynamics and long-term prognosis in patients with right ventricular (RV) acute myocardial infarction (AMI) using Fourier phase and amplitude analysis of radionuclide angiocardiographic scanning. In 143 patients with RV AMI, delayed phase and low amplitude in radionuclide RV images persisted in 54 patients (persistent RV dysfunction group) 3 months after AMI, but disappeared in the remaining 89 patients (improved RV function group). No significant differences were present in RV dimensions, left ventricular (LV) wall motion, LV ejection fraction, or RV ejection fraction between these groups during the acute phase. At 3 months, RV dimension and LV and RV wall motion indexes were significantly higher (p = 0.0292, p = 0.0124, p<0.0001, respectively), and LV and RV ejection fractions were lower (p = 0. 0174 and p = 0.0008, respectively) in the persistent RV dysfunction group. Percutaneous transluminal coronary angioplasty in the acute phase was performed in a smaller group of patients (15% vs. 34%, p = 0.0223), and the degree of residual stenosis in the proximal right coronary artery was significantly greater in the persistent RV dysfunction group than in the improved RV function group (82+/-22% vs. 53+/-30%, p<0.0001). The 8-year survival rate was significantly lower in the persistent RV dysfunction group (p<0.0001). Persistent abnormality of phase and amplitude in radionuclide RV images was a significant independent predictor of long-term survival (odds ratio 10.42; 95% confidence interval 3.65 to 29.71; p<0.0001). Radionuclide angiocardiographic Fourier phase and amplitude scanning can detect persistent RV dysfunction in patients with RV AMI and can predict patient outcome.

[Prognostic significance of advanced atrioventricular block in patients with acute myocardial infarction]

BACKGROUND

Advanced atrioventricular block (AB) during acute myocardial infarction (AMI), characterizes a high-risk subgroup of patients. Our aim was to determine the prognostic significance of AB and its possible peculiarities in relation to infarction localization and/or the thrombolytic therapy.

PATIENTS AND METHODS

The prospective study involved 1,239 patients with AMI. We studied clinical characteristics, as well as indexes of infarct size, short and long-term complications.

RESULTS

AB was present in 85 (6.8%) patients and was more often associated with: previous treatment with diuretics, diabetes, inferior localisation, higher number of ECG leads with elevated ST segment, and higher peak of CK. The AB was associated with a higher mortality: in-hospital (27% vs 10.6%; p < 0.01)) and after one-year (31.7% vs 19.4%; p < 0.05). Patients with AB had a different in-hospital mortality depending on anterior or inferior infarct localization (66% vs 18.5%; p < 0.001, respectively). In patients receiving thrombolytic treatment (n = 681), the duration of AB was shorter and in-hospital mortality was lower (13.7% vs 47%, p < 0.11) than that occurred in patients without this treatment (n = 558). AB had independent value for predicting in-hospital mortality (OR: 3.56; 95% CI: 1.84-6.90) and one-year mortality (OR: 2.77; 95% CI: 1.52-5.04).

CONCLUSIONS

AB is associated with larger infarcts and higher incidence of complications. The prognosis is especially poor when it is presented associated with anterior infarction and/or in patients without thrombolytic treatment. AB is a variable with independent prognostic value on the mortality.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

Complete atrioventricular block complicating acute myocardial infarction in the thrombolytic era. SPRINT Study Group and the Israeli Thrombolytic Survey Group. Secondary Prevention Reinfarction Israeli Nifedipine Trial

OBJECTIVES

We assessed the incidence, associated clinical parameters and prognostic significance of complete atrioventricular block (CAVB) complicating acute myocardial infarction (AMI) in the thrombolytic era and compared them to data from the prethrombolytic era.

BACKGROUND

The introduction of new therapeutic modalities to treat AMI, aimed to enhance coronary reperfusion and to limit myocardial necrosis, was expected to decrease the incidence of CAVB and to improve prognosis. However, there are only limited data regarding the incidence and the prognosis of AMI patients with CAVB in the thrombolytic era.

METHODS

Data from 3,300 patients from the Israeli Thrombolytic Surveys (prospective, nationwide surveys of consecutive patients with AMI in all 25 coronary-care units in Israel in 1992 and 1996) were analyzed and compared with data from 5,788 patients included in the SPRINT (Secondary Prevention Reinfarction Israeli Nifedipine Trial) Registry (1981 to 1983).

RESULTS

During the 1990s, the incidence of CAVB was 3.7% compared with 5.3% in the 1980s, p = 0.0007. In the 1990s, mortality of patients with CAVB was significantly higher than in those without CAVB at 7 days (odds ratio [OR] = 4.05 95% CI [confidence interval] 2.34 to 6.82, 30 days OR = 3.98 [95% CI 2.44 to 6.43] and one-year hazard ratio [HR] = 2.36, [95% CI 1.68 to 3.30]) and similar in thrombolysis-treated and not-treated patients. Mortality of patients with CAVB has not changed significantly between the two periods; seven-day OR = 0.82 (95% CI 0.46 to 1.43); 30-day OR = 0.78 (95% CI 0.45 to 1.33) and one-year HR = 0.79 (95% CI 0.54 to 1.56), respectively, in the 1990s as compared to a decade earlier.

CONCLUSIONS

The incidence of CAVB complicating AMI is lower in the thrombolytic era than in the prethrombolytic era. Mortality among patients with CAVB is still high and has not declined within the last decade. The AMI patients who develop CAVB in the thrombolytic era have significantly worse prognosis than do patients without CAVB.

[The clinical management guidelines of the Sociedad Española de Cardiología in acute myocardial infarct]

In the recent years, new possibilities have emerged in the diagnosis and management of acute myocardial infarction with ST segment elevation and its complications. Moreover, a deep transformation has taken place in the health care system organization, particularly in aspects related to care of patients presenting non-traumatic chest pain, both in pre-hospital and hospital areas. All these issues warrant a consensus document in Spain dealing with the role that these important changes should play in the whole management of myocardial infarction patients. This document revises and updates all the main clinical issues of acute myocardial infarction patients from the moment they contact with the health care system outside the hospital until they return home, after staying at the coronary care unit and the general hospitalization ward. All those aspects are considered not only in the uncomplicated myocardial infarction but also in the complicated one. This review also includes a set of recommendations on structural and organisational aspects, mainly referred to the prehospital and emergency levels.

Comparison of results of early reperfusion in patients with inferior wall acute myocardial infarction with and without complete atrioventricular block

We investigated the effect of reperfusion in patients with complete atrioventricular block within 6 hours after the onset of inferior wall acute myocardial infarction. Early reperfusion may promote the restoration of normal sinus rhythm and effectively reduce infarct size in these patients.

Electrocardiographic criteria for predicting the culprit artery in inferior wall acute myocardial infarction

Two patterns of the QRS complex in the lateral lead aVL on the admission electrocardiograms of patients with inferior wall acute myocardial infarction (AMI) were correlated with the culprit artery. S/R wave ratio < or =1/3 with ST depression < or =1 mm was found to be a sensitive and specific marker for left circumflex artery AMI, whereas S/R-wave ratio >1/3 with ST-segment depression >1 mm was suggestive of right coronary artery AMI.

Right Ventricular Infarction: Contribution of Echocardiography to Diagnosis and Management

Right ventricular infarction (RVI) is associated with nearly one third of patients who have inferior myocardial infarction (MI). The classic triad of hypotension, clear lung fields, and increased jugular venous pressure in the setting on inferior MI is highly suggestive of RVI. Direct visualization of the RV and left ventricular chambers on two-dimensional echocardiography allows early diagnosis by demonstration of predominant RV asynergy (akinesis plus dyskinesis), RV dilation, and decreased RV ejection fraction. The extent of RV involvement varies widely and correlates with outcome. Serial two-dimensional echocardiography and Doppler are also valuable in short- and long-term management, to detect complications, and to assess outcome.

Antecedent angina pectoris as a predictor of better functional and clinical outcomes in patients with an inferior wall acute myocardial infarction

We examined whether angina pectoris (AP) occurring shortly before the onset of acute myocardial infarction (AMI) can render the right ventricle and the conducting tissue resistant to ischemia in 75 patients with an inferior wall AMI. Each patient had total occlusion in the proximal right coronary artery and underwent successful coronary angioplasty < or =24 hours from the onset. We divided patients into 2 groups based on presence or absence of antecedent AP < or =24 hours before the system onset: group 1 (absent) = 57 patients; group 2 (present) = 18 patients. Collateral circulation was more frequently observed in group 2 than in group 1 (group 1 vs 2, 28% vs 61%, p <0.01). Elevation in ST segment > or =1 mm in lead V4R, hemodynamic right ventricular dysfunction, and frequency of high-degree heart block were more frequent in group 1 than in group 2 (75% vs 44%, 79% vs 39%, 53% vs 11%, p <0.05, respectively). Multivariate analysis demonstrated that antecedent AP is the only factor related to these complications. Thus, episodes of AP occurring shortly before onset may restrain development of ischemic damage of the right ventricle and conducting tissue, and are associated with better clinical and functional outcomes among patients with an inferior wall AMI.

Electrocardiographic patterns in acute inferior myocardial infarction with and without right ventricle involvement: classification, diagnostic and prognostic value, masking effect

BACKGROUND

In acute inferior myocardial infarction (AIMI), the ST depression from V1 to V4 has been the subject of many papers, while the ST changes in other leads, their association, and the right ventricular (RV) involvement have been studied less.

HYPOTHESIS

This study was performed to contribute to the meaning of the ST changes and RV involvement in AIMI.

METHODS

Seventy-one patients, admitted within 6 h from symptom onset, all thrombolysed, were enrolled. We classified them according to ST patterns and RV involvement. We divided the right coronary artery into three segments, considering the origin of RV branch and the crux as dividing points. We established a coronary score attributing 2 points to each terminal branch. Comparisons were performed between the electrocardiographic (ECG) findings at onset, the creatine phosphokinase (CPK) peaks, the radionuclide ejection fractions, and the coronary angiographies.

RESULTS

We found that the ST changes give indications regarding the site, extension, and extent of AIMI; RV involvement can mask posterior extension, points to the right coronary as the culprit vessel (100%), and, with high probability, indicates the proximal segment as the site of the lesion; the ECG signs of isolated AIMI indicate a peripheral obstruction; and a collateral circulation may appear relatively early.

CONCLUSIONS

Our findings prove the diagnostic and prognostic value of the ST changes and RV involvement at the onset of AIMI and suggest that the higher in-hospital mortality and complication rates found with RV involvement and reported in the literature are related more to posterior extension, masked by RV involvement than to this involvement per se. Furthermore, these findings prove the clinical value of our classification of the AIMIs and distinction in segments of the right coronary artery.

New electrocardiographic criteria for predicting the site of coronary artery occlusion in inferior wall acute myocardial infarction

In patients with inferior wall acute myocardial infarction (AMI), the site of the culprit lesion is an important determinant of outcome. Patients with right ventricular infarction have a poor prognosis, whereas those with occlusion of the left circumflex coronary artery (LCx) have a good prognosis. Therefore, we assessed whether standard 12-lead electrocardiograms obtained on admission could identify the site of coronary artery occlusion, (i.e., a site proximal to the origin of the right ventricular branch of the right coronary artery [RCA], a site distal to the origin of the right ventricular branch of the RCA, or a site in the LCx). The ratio of ST depression in lead V3 to ST elevation in lead III (V3/III ratio) was evaluated immediately before coronary angiography in 152 patients with a first inferior wall AMI confirmed by coronary angiography within 12 hours after the onset of symptoms. For occlusion of the proximal RCA, distal RCA, and LCx, V3/III ratio was 0.2+/-0.3, 0.8+/-0.5, and 2.5+/-2.5 (p = 0.0001), respectively. The V3/III ratio <0.5 identified proximal RCA occlusion, 0.5 <V3/III ratio < or = 1.2 identified distal RCA occlusion, and 1.2 <V3/III ratio identified LCx occlusion with sensitivities of 91%, 84%, and 84%, and specificities of 91%, 93%, and 95%, respectively. We conclude that the V3/III ratio is useful in predicting the site of coronary artery occlusion in patients with inferior wall AMI.

Comparison of thrombolytic therapy and primary coronary angioplasty with liberal stenting for inferior myocardial infarction with precordial ST-segment depression: immediate and long-term results of a randomized study

OBJECTIVES

The aim of the study was to compare randomly assigned primary angioplasty and accelerated recombinant tissue plasminogen activator (rt-PA), in patients with "high-risk" inferior acute myocardial infarction (ST-segment elevation in the inferior leads and ST-segment depression in the precordial leads).

BACKGROUND

The ST-segment depression in the precordial leads is a marker of severe prognosis in patients with inferior myocardial infarction. The comparative outcome of treatment with primary angioplasty or lysis with accelerated rt-PA has not been investigated.

METHODS

One hundred and ten patients within 6 h of symptoms were randomized to either treatment. To assess the in-hospital and 1-year outcome of both treatments the following results were compared: death or nonfatal infarction, recurrence of angina, left ventricular ejection fraction (LVEF), and the need for repeat target vessel revascularization (TVR).

RESULTS

In patients treated with angioplasty (55) and rt-PA (55) the rate of in-hospital mortality and reinfarction was 3.6% versus 9.1% (p=0.4). Recurrence of angina was 1.8% versus 20% (p=0.002), new TVR was used in 3.6% versus 29.1% (p=0.0003), and the LVEF (%) at discharge was 55.2+/-9.5 versus 48.2+/-9.9 (p=0.0001). There were no hemorrhagic strokes, no emergency coronary artery bypass graft (CABG) and identical (5.5%) need for blood transfusions. At 1 year, the incidence of death, reinfarction or repeat TVR was 11% in the percutaneous transluminal coronary angioplasty (PTCA) group versus 52.7% in the rt-PA group (log-rank 22.38, p < 0.0001).

CONCLUSIONS

Primary angioplasty is superior to accelerated rt-PA in terms of both myocardial preservation and reduction of in-hospital complications in patients with inferior myocardial infarction and precordial ST-segment depression. Primary angioplasty also yields a better long-term event-free survival.

Effect of aminophylline in patients with atropine-resistant late advanced atrioventricular block during acute inferior myocardial infarction

BACKGROUND

Advanced atrioventricular (AV) block is a frequent complication in patients with acute inferior myocardial infarction (AIMI). This conduction abnormality is associated with narrow QRS complex in conducted or junctional escape beats, suggesting that the site of block is the AV node; however, its pathophysiology has not been properly established.

HYPOTHESIS

This study investigated the effect of aminophylline in eight patients (5 men, 3 women, age range 51 to 78 years, mean 67.5 +/- 8.8 years) with atropine-resistant late advanced AV block during AIMI.

METHODS

Advanced AV block was late in appearance in all patients, starting 2 to 5 days after AIMI, and consisted of second-degree Mobitz II type in two patients and of complete AV block in six patients; all patients had narrow QRS complexes. Before aminophylline administration, all patients had a temporary pacemaker installed which was switched off throughout the study. They were given intravenous atropine (1 mg) that was found to be ineffective. One-half h after atropine, the first aminophylline injection (240 mg) was given intravenously over 10 min. One h following the first injection, a second aminophylline dose (240 mg) was administered. Electrocardiographic rhythm strips were obtained before and after drug administration, and the type of AV block and atrial and ventricular rate were noted.

RESULTS

Aminophylline restored 1:1 conduction with first-degree AV block in six patients, Mobitz I AV block in one patient, and normal sinus rhythm in one patient. Mean atrial and ventricular rates before aminophylline were 104 +/- 16 beats/min and 57 +/- 9 beats/min, respectively, and after drug administration 95 +/- 25 beats/min and 89 +/- 17 beats/min, respectively, (p = 0.012).

CONCLUSION

These results indicate that aminophylline improves AV conduction in atropine-resistant late advanced AV block complicating AIMI.

Effects of thrombolytic therapy in acute inferior myocardial infarction with or without right ventricular involvement. HIT-4 Trial Group. Hirudin for Improvement of Thrombolysis

OBJECTIVES

This study assessed the prognostic impact of right ventricular involvement (RVI) in streptokinase-treated patients with inferior acute myocardial infarction (AMI) stratified for small or large AMI.

BACKGROUND

Only scant data exist from small studies about the impact of reperfusion therapy on survival in patients with RVI during inferior AMI.

METHODS

Right ventricular involvement was assessed by ST-segment elevation > or =0.1 mV in lead V4R and infarct size by the extent of ST-segment deviation on the baseline electrocardiogram: small AMI=sum ST-segment elevation < or =0.8 mV and no precordial ST-segment depression (small ST); large AMI=presence of precordial ST-segment depression or sum ST-segment elevation >0.8 mV (large ST) in 522 inferior AMI patients of the Hirudin for Improvement of Thrombolysis (HIT-4) Trial. In 187 patients, 90-min coronary angiography was performed.

RESULTS

Right ventricular involvement was present in 169 patients (32%). Higher 30-day cardiac mortality rates with RVI (5.9% vs. 2.5%) were related to larger infarct size rather than to RVI. For large ST, a proximal right coronary artery lesion was observed in 52% with and in 23% without RVI. Patency rates at 90 min were similar (54% vs. 52%). In the 28% of patients who had small ST, cardiac mortality was less than 1% irrespective of the presence of RVI. Coronary artery lesions were mostly located distally. Patency rates were 27% with and 80% without RVI.

CONCLUSIONS

ST-segment elevation of > or =0.1 mV in V4R in inferior AMI patients is associated with larger infarct size and higher 30-day mortality rates. Right ventricular involvement is not an independent predictor of survival. In patients with small ST, cardiac mortality is low, even if ST V4R is > or =0.1 mV.

Thrombolytic eligibility

The Fibrinolytic Therapy Trialists' Collaborative Group has demonstrated that patients without clear contraindications who present with ischaemic chest pain within 12 hours of the onset of symptoms and who have ST segment elevation or bundle branch block on their electrocardiogram (ECG), will benefit from thrombolytic therapy. Therefore the treatment of patients presenting with ischaemic chest pain is guided by the initial ECG. This paper addresses the question of thrombolytic eligibility in several subsets of patients who may benefit from treatment. It also explores the data which confirm the benefit for patients presenting with an inferior myocardial infarction and for those presenting from six-12 hours after the onset of symptoms. In conclusion, thrombolytic therapy should not be routinely withheld from diabetic or elderly patients, menstruating women and patients who have had cardiopulmonary resuscitation.

Usefulness of ST-segment elevation in lead III exceeding that of lead II for identifying the location of the totally occluded coronary artery in inferior wall myocardial infarction

The presence of ST-segment elevation in lead III exceeding that of lead II, particularly if combined with ST elevation in lead V1, proved to be a powerful marker for occlusion of the proximal or midportion of the right coronary artery. These findings helped to determine the extent of myocardium at risk in inferior wall myocardial infarction and may further guide the decision to administer thrombolytics.

ST-segment elevation in right precordial leads implies depressed right ventricular function after acute inferior myocardial infarction

BACKGROUND

The prognosis of acute inferior myocardial infarction is worse when it is complicated by right ventricular infarction. ST elevation in the right precordial leads is one of the reliable methods for detecting acute right ventricular infarction. The purpose of the study was to examine the relation between ST elevation in the right precordial electrocardiographic leads during acute inferior infarction and the severity of right ventricular systolic dysfunction.

METHODS

This study analyzed the relation between ST elevation > or = 0.1 mV in V4R and the severity of right ventricular systolic dysfunction in 43 consecutive patients (men/women: 35/8; average age 62+/-9 years) with acute inferior myocardial infarction with a rapid-response Swan-Ganz catheter to measure the right ventricular ejection fraction (RVEF).

RESULTS

RVEF was significantly lower in patients with ST elevation (n = 18) than in those without (n = 25) (33%+/-6% vs 40%+/-9%, p = 0.010). If the infarct-related lesion was located in the proximal right coronary artery, RVEF tended to be lower than if the lesion was located in the distal right coronary artery or the left circumflex coronary artery (33%+/-10% vs 37%+/-9% vs 42%+/-9%, p = 0.101). Logistic regression analysis demonstrated that ST elevation in V4R was the only independent predictor of depressed RVEF (odds ratio = 5.31, 95% confidence interval = 1.28 to 22.1, p = 0.022).

CONCLUSION

ST elevation in lead V4R during acute inferior myocardial infarction predicts right ventricular systolic dysfunction.

Diagnostic approach in exercise testing to detect a significant narrowing of the left anterior descending coronary artery in inferior vs posterior myocardial infarction

To detect a significant narrowing of the left anterior descending artery in patients with inferior/posterior myocardial infarction, 200 patients underwent standard exercise testing. Age, gender, and grade of stenosis of the left anterior descending artery were similar in 138 patients with inferior myocardial infarction and 62 with posterior myocardial infarction. In patients with left anterior descending artery stenosis, there were more lateral leads with ST-segment depression (1.8+/-1.0 vs 1.1+/-1.1; p<0.01) and fewer anterior leads with ST-segment depression (2.1+/-1.4 vs 2.9+/-1.4; p=0.02) in those with inferior myocardial infarction than in those with posterior myocardial infarction. Applying the criterion of exercise-induced ST-segment depression > or = 0.1 mV, sensitivities and specificities in detecting left anterior descending artery stenosis were 98% and 21% respectively in inferior myocardial infarction and 94% and 26% respectively in posterior myocardial infarction. In contrast, discriminant analysis revealed sensitivities and specificities of 77% and 91% respectively in inferior myocardial infarction and 71% and 81% respectively in posterior myocardial infarction using the variables related to severity of inducible ischemia and lateral and anterior lead ST-segment depression. These results indicate that a multivariate approach underscoring the site of myocardial infarction can help in identifying stenosis of the left anterior descending artery in patients with inferior/posterior myocardial infarction.

Usefulness of pulmonary regurgitation Doppler tracings in predicting in-hospital and long-term outcome in patients with inferior wall acute myocardial infarction

Right ventricular (RV) involvement is frequent during inferior wall acute myocardial infarction (AMI) and has been reported as a risk factor for in-hospital morbidity and mortality. The objectives of the present study were: (1) to evaluate in-hospital events in patients with and without RV involvement as diagnosed by abnormal flow characteristics derived from pulmonary regurgitation (PR) analysis (pressure half-time of PR, PHT(PR) < or = 150 ms and the lowest mid-diastolic to peak early diastolic velocity ratio, Vmin/Vmax < or = 0.5); and (2) to determine the influence of RV involvement in complications at long-term follow-up. Among 126 consecutively admitted patients with inferior wall AMI (mean age, 58 +/- 13 years), 101 had PR. We determined the prognostic significance of in-hospital and long-term events for the following variables: age > or = 65 years, ST-segment elevation > or = 1 mm in lead V4R, RV dilation, PHT of PR < or = 150 ms and Vmin/Vmax < or = 0.5, thrombolytic therapy, 3-vessel disease, and diabetes mellitus. We found that the PR derived Doppler index (PHT of PR < or = 150 ms and Vmin/Vmax < or = 0.5) was the only predictor of overall in-hospital clinical events (hazards ratio, 2.7, 95% confidence interval, 1.2 to 6.1, p = 0.016). At long-term follow-up (mean: 20 +/- 12 months, range 12 to 69), event-free survival analysis showed that age > or = 65 years was the only predictor of any event (relative risk, 3.7, 95% confidence interval, 2.1 to 6.3, p < 0.0001). Thus, RV involvement diagnosed with the use of PR flow-derived variables is an accurate and independent predictor of in-hospital complications. However, RV involvement does not influence long-term prognosis.

Right heart ischemia: pathophysiology, natural history, and clinical management

Right ventricular (RV) ischemia occurs in 50% of patients with acute inferior myocardial infarction, and may result in severe hemodynamic compromise associated with poor clinical outcome. Acute right coronary artery (RCA) occlusion proximal to the RV branches results in right ventricular free wall (RVFW) dysfunction. The ischemic, dyskinetic RVFW exerts mechanically disadvantageous effects on biventricular performance. Depressed RV systolic function leads to a decrease in transpulmonary delivery of left ventricular (LV) preload, resulting in diminished cardiac output. The ischemic right ventricle is stiff, dilated, and volume dependent, resulting in pandiastolic RV dysfunction and septally-mediated alterations in LV compliance, which are exacerbated by elevated intrapericardial pressure. Under these conditions, RV pressure generation and output are dependent on LV-septal contractile contributions, governed by both primary septal contraction and paradoxical septal motion. When the culprit coronary lesion is distal to the right atrial (RA) branches, augmented RA contractility enhances RV performance and optimizes cardiac output. Conversely, more proximal occlusions result in ischemic depression of RA contractility, which impairs RV filling, thereby resulting in further depression of RV performance and more severe hemodynamic compromise. Bradyarrhythmias limit the output generated by the rate-dependent noncompliant ventricles. Patients with right ventricular infarction and hemodynamic compromise often respond to volume resuscitation and restoration of a physiological rhythm. Vasodilators and diuretics should generally be avoided. In some, parenteral inotropic stimulation may be required. The right ventricle appears to be relatively resistant to infarction and has a remarkable ability to recover even after prolonged occlusion. Therefore, the term RV infarction appears to be somewhat of a misnomer, for in most patients a substantial proportion of acute RV dysfunction represents ischemic but viable myocardium. Although RV performance improves spontaneously even in the absence of reperfusion, recovery of function may be slow and associated with high in-hospital mortality. Reperfusion enhances the recovery of RV performance and improves the clinical course and survival of patients with ischemic RV dysfunction.

Association between anterior ST depression and increased myocardial salvage following reperfusion therapy in patients with inferior myocardial infarction

PURPOSE

To determine electrocardiographic features associated with myocardial salvage following reperfusion therapy in patients with inferior myocardial infarction.

PATIENTS AND METHODS

Ninety-two consecutive patients with acute inferior myocardial infarction were treated with reperfusion therapy in a tertiary care center. Several features were measured on the presenting electrocardiogram, including the presence or absence of ST depression in the chest leads and the total magnitudes of ST elevation or depression, and were then evaluated for their association with myocardial salvage. Myocardial salvage (% of left ventricle) was the difference between myocardium at risk and final infarct size. Tomographic myocardial perfusion imaging with technetium-99m sestamibi was performed acutely to measure myocardium at risk and repeated prior to hospital discharge to measure final infarct size.

RESULTS

The amount of myocardium at risk of infarction in the 92 patients was 19.1%+/-11.3% (range 1% to 68%), and the final infarct size was 10.6%+/-10.0% (range 0% to 45%). Thus, myocardial salvage in the 92 patients was 8.5%+/-8.4% (range -11% to 35%) of the left ventricle, or 0.51+/-0.38 (range 0.0 to 1.0) when expressed as a fraction of the myocardium at risk (salvage index). The presence or absence of anterior ST depression was the only one of seven electrocardiographic variables that was associated with myocardial salvage. Myocardial salvage was significantly greater in patients with anterior ST depression compared with those without it (10.6%+/-9.0% versus 5.9%+/-6.7%, P=0.025). Myocardium at risk was significantly greater in patients with anterior ST depression compared with those without the depression (22.8%+/-12.2% versus 14.6%+/-8.3%, P=0.0006), and infarct size tended to be larger (12.1%+/-10.4% versus 8.7%+/-9.4%, P=0.10). Myocardial salvage as a fraction of the myocardium at risk (salvage index) was similar between the two patient groups (0.52+/-0.37 versus 0.50+/-0.39, P=NS).

CONCLUSION

The presence of anterior ST depression during inferior myocardial infarction identifies a group of patients with the potential for greater myocardial salvage with reperfusion therapy. Such patients derive greater absolute benefit from reperfusion therapy because they have a larger amount of myocardium at risk, although their response to therapy (salvage index) is not intrinsically different.

Change in ST segment elevation 60 minutes after thrombolytic initiation predicts clinical outcome as accurately as later electrocardiographic changes

OBJECTIVE

To compare prospectively the prognostic accuracy of a 50% decrease in ST segment elevation on standard 12-lead electrocardiograms (ECGs) recorded at 60, 90, and 180 minutes after thrombolysis initiation in acute myocardial infarction.

DESIGN

Consecutive sample prospective cohort study.

SETTING

A single coronary care unit in the north of England.

PATIENTS

190 consecutive patients receiving thrombolysis for first acute myocardial infarction.

INTERVENTIONS

Thrombolysis at baseline.

MAIN OUTCOME MEASURES

Cardiac mortality and left ventricular size and function assessed 36 days later.

RESULTS

Failure of ST segment elevation to resolve by 50% in the single lead of maximum ST elevation or the sum ST elevation of all infarct related ECG leads at each of the times studied was associated with a significantly higher mortality, larger left ventricular volume, and lower ejection fraction. There was some variation according to infarct site with only the 60 minute ECG predicting mortality after inferior myocardial infarction and only in anterior myocardial infarction was persistent ST elevation associated with worse left ventricular function. The analysis of the lead of maximum ST elevation at 60 minutes from thrombolysis performed as well as later ECGs in receiver operating characteristic curves for predicting clinical outcome.

CONCLUSION

The standard 12-lead ECG at 60 minutes predicts clinical outcome as accurately as later ECGs after thrombolysis for first acute myocardial infarction.

Value of leads V7-V9 in diagnosing posterior wall acute myocardial infarction and other causes of tall R waves in V1-V2

Left posterolateral chest leads (V7, V8, V9) helped distinguish the multiple causes of tall R waves in V1 and/or V2, diagnosed true posterior myocardial infarction when standard leads did not, and identified the presence or absence of posterior injury in patients with inferior infarction.

Revisiting reperfusion therapy in inferior myocardial infarction

Although thrombolytic therapy for acute myocardial infarction (MI) is recommended without regard for infarct location, treatment results are less impressive for inferior than for anterior MI because the amount of myocardium at risk is smaller and less strategically located, and the mortality risk is lower. Whereas the risks associated with anterior MI are relatively constant, high risk subsets of patients with an inferior MI can be identified by simple electrocardiographic criteria, including left precordial ST segment depression, complete atrioventricular heart block and right precordial ST segment elevation. Unfortunately, none of the placebo-controlled, randomized trials have analyzed the benefit of thrombolytic therapy for inferior MI in high risk versus low risk subsets. Thrombolytic therapy should be more successful in reducing infarct size and decreasing mortality in high risk patients with an inferior MI. Thrombolytic therapy may not decrease hospital mortality in low risk patients (baseline risk 2% to 4%) or those with symptom duration > 6 h. Whereas it is arguable whether coronary angioplasty is superior to thrombolytic therapy in anterior MI, there are no mortality data to support using angioplasty as a primary or rescue reperfusion strategy instead of thrombolytic therapy in inferior MI, unless thrombolytic contraindications are present or the patient is in cardiogenic shock.

Impact of early accelerated dose tissue plasminogen activator on in-hospital patency of the infarcted vessel in patients with acute right ventricular infarction

OBJECTIVE

To assess the efficacy of early accelerated dose tissue plasminogen activator on in-hospital patency of the infarct related artery in patients with inferior myocardial infarction with and without right ventricular involvement.

DESIGN

Single centre prospective assessment before discharge of infarct related vessel patency after early thrombolysis.

SETTING

Tertiary cardiac referral centre at a university hospital.

PATIENTS AND METHODS

90 consecutive unselected patients with acute myocardial infarction, of whom 35 (39%) had electro-cardiographic evidence of right ventricular involvement (ST segment elevation greater than 0.1 mV in right precordial lead V4R), were studied. All patients received accelerated dose tissue plasminogen activator 100 mg within six hours from the onset of symptoms and had control angiography before discharge.

MAIN OUTCOME MEASURES

Infarct related coronary artery patency using the Thrombolysis in Myocardial Infarction (TIMI) grading system before discharge. Incidence of prolonged systemic hypotension, sinus bradycardia, complete atrioventricular block, and ventricular tachyarrhythmia during early hospitalisation.

RESULTS

Despite aspirin and bolus heparinisation before thrombolysis and high dose heparinisation thereafter for at least 48 hours the infarct related artery was more likely to be occluded (TIMI 0 or 1 flow) in patients with right ventricular involvement than in those without (69 v 29%, P < 0.001), as shown by control angiography performed a mean of 12.8 days after thrombolysis. These findings may be explained, at least in part, by predominant involvement of the proximal right coronary artery (66 v 31%, P < 0.05) and a low cardiac output syndrome, being indirectly reflected by a high incidence of prolonged hypotension (26 v 7%, P = 0.02), bradycardia (34 v 14%, P = 0.03), and complete atrioventricular block (37 v 5%, P = 0.0001).

CONCLUSION

Primary angioplasty should be considered as the treatment of choice in patients with acute inferior infarction with right ventricular involvement because of the high failure rate of thrombolysis.

Maximal precordial ST-segment depression in leads V4-V6 in patients with inferior wall acute myocardial infarction indicates coronary artery disease involving the left anterior descending coronary artery system

BACKGROUND

In inferior wall acute myocardial infarction, maximal ST-segment depression in left precordial leads (V4-V6) has been shown to be associated with increased in-hospital mortality, presumably due to coronary artery disease involving the left anterior descending coronary artery system.

METHODS

We measured ST-segment deviation from baseline in the initial electrocardiogram of patients with inferior wall acute myocardial infarction, who subsequently underwent coronary angiography during their in-hospital stay. Patients were divided into three groups: (I) No precordial ST-segment depression (n = 34). (II) Maximal precordial ST-segment depression in leads V1-V3 (n = 44). (III) Maximal precordial ST-segment depression in leads V4-V6 (n = 14).

RESULTS

The left anterior descending coronary artery or its diagonal branch were stenosed (> 50%) in 32%, 41%, and 71% of patients in groups I, II, and III, respectively (p = 0.04), and severely stenosed (> 70%) in 18%, 18% and 57% of patients in the respective groups (p = 0.007).

CONCLUSION

In patients with inferior wall acute myocardial infarction, maximal precordial ST-segment depression in leads V4-V6 is suggestive of severe coronary artery disease involving the left anterior descending coronary artery or its diagonal branch.

Prognostic significance of precordial ST segment depression on admission electrocardiogram in patients with inferior wall myocardial infarction

OBJECTIVES

This study assessed retrospectively the correlation between the pattern of precordial ST segment depression on the admission electrocardiogram (ECG) and hospital mortality in patients with an inferior myocardial infarction treated with intravenous thrombolytic therapy.

BACKGROUND

Previous studies have shown that in acute inferior myocardial infarction, ST segment depression in the precordial leads is associated with increased hospital mortality. However, the significance of the different patterns of precordial ST segment depression has been evaluated in only two previous studies.

METHODS

The study included 1,321 patients (1,020 men) who enrolled in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) trial in Israel and received intravenous thrombolytic therapy. Patients with an ST segment elevation > or = 0.1 mV in at least two of the inferior leads were included. Patients were classified into four groups on the basis of their admission ECG: group I = patients with no precordial ST segment depression (n = 346); group II = those for whom the sum of ST segment depression in leads V1 to V3 was greater than that in leads V4 to V6 (n = 700); group III = those for whom the sum of ST depression in leads V1 to V3 was equal to that in leads V4 to V6 (n = 162); group IV = those with maximal ST depression in leads V4 to V6 (n = 113).

RESULTS

The overall hospital mortality rate was 3.6% (48 patients): for groups I, II, III and IV it was 2.9%, 2.8%, 4.3% and 9.7%, respectively. Multivariable logistic regression analysis confirmed that hospital mortality was independently associated with the pattern of precordial ST segment depression. The odd ratios in group IV relative to group I was 2.78 (95% confidence interval 1.26 to 6.13, p = 0.007).

CONCLUSIONS

The risk of mortality is higher in patients with an inferior myocardial infarction and maximal ST segment depression in precordial leads V4 to V6 versus precordial leads V1 to V3 on the admission ECG.

Prognostic significance of precordial ST segment depression during inferior myocardial infarction in the thrombolytic era: results in 16,521 patients

OBJECTIVES

We examined the prognostic significance of precordial ST segment depression among patients with an acute inferior myocardial infarction.

BACKGROUND

Although precordial ST segment depression has been associated with a poor prognosis, this correlation has not been adequately quantified, partly because of small sample sizes and methodologic limitations in previous studies.

METHODS

We examined the clinical and angiographic outcomes of 16,521 patients with an acute inferior myocardial infarction who underwent thrombolysis in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) study. Patients were classified into those without precordial ST segment depression (n = 6,422 [38.9%]), those with ST segment depression in leads V1 to V3 only (n = 5,850 [35.4%]), those with ST segment depression in leads V4 to V6 only (n = 876 [5.3%]) and those with ST segment depression in both leads V1 to V3 and leads V4 to V6 (n = 3,373 [20.4%]) on initial electrocardiography. Outcome measures included postinfarction complications (second- or third-degree heart block, congestive heart failure or shock) and 30-day and 1-year mortality.

RESULTS

Patients with precordial ST segment depression had larger infarctions, more postinfarction complications and a higher mortality rate than those without precordial ST segment depression (4.7% vs. 3.2% at 30 days; 5.0% vs. 3.4% at 1 year; both p < 0.001), regardless of whether ST segment depression was noted in leads V1 to V6 or in leads V4 to V6. The magnitude of precordial ST segment depression (sum of leads V1 to V6) added significant independent prognostic information after adjustment for clinical risk factors; the risk of 30-day mortality increased by 36% for every 0.5 mV of precordial ST segment depression.

CONCLUSIONS

Assessment of the magnitude of precordial ST segment depression is useful for acute risk stratification in patients with an inferior myocardial infarction.

Electrocardiographic identification of the infarct-related artery in acute inferior myocardial infarction

Differentiation between left circumflex occlusion and right coronary occlusion in inferior acute myocardial infarction is a common clinical problem. This study investigated new electrocardiographic markers for differentiation, including T wave inversion, and individual inferior and precordial lead ST level, versus the traditional criterion of lateral ST elevation. In 95 angiographically characterised patients, ST elevation in lateral chest lead V5 or V6 had a sensitivity of 56% and specificity of 92% to predict left circumflex related acute myocardial infarction while the absence of lateral T inversion in I and AVL was even more sensitive (89%) though less specific (74%). A criterion of ST depression in V1 > 0.1 mV has a sensitivity of 61% and specificity of 84% whereas a criterion of ST level in III minus II < or = 0.1 mV has a sensitivity of 94% and specificity of 37% in predicting left circumflex related acute myocardial infarction. These criteria were then tested in another 49 patients subsequently recruited with inferior acute myocardial infarction. Useful parameters that discriminated left circumflex related acute myocardial infarction from right coronary related acute myocardial infarction include lateral ST elevation (38% vs. 7%, P < 0.05), absence of lateral T inversion (50% vs. 15%, P < 0.05), and ST depression in V1 of more than 0.1 mV (50% vs. 7%, P < 0.05). The present study revealed new electrocardiographic clues to suggest a left circumflex related inferior acute myocardial infarction other than lateral ST elevation. However, it should be noted that no single electrocardiographic variable or their combinations could identify the infarct-related artery with complete certainty.