Is the shortening of the QTc interval in Q-wave leads showing ST segment shift during exercise testing a new ECG marker of myocardial ischemia and viability in patients with previous anterior myocardial infarction?

PURPOSE: To evaluate whether the shortening of the QTc-interval, measured in Q-wave leads showing ST segment elevation during exercise testing may be a marker of stress-induced transmural ischemia (and indirectly of myocardial viability) in the infarct zone in patients with prior Q-wave anterior myocardial infarction. METHODS: We evaluated 15 consecutive patients (Group A) with previous anterior myocardial infarction presenting these peculiarities: 1) ST segment elevation over Q waves during exercise testing; 2) critical (> 75%) stenosis of LAD; 3) evidence by echocardiography and stress-redistribution-reinjection 201thallium myocardial scintigraphy (SRR201TIMS) of viable myocardium in the infarct zone (akinetic segments with normal echo-reflectivity plus > 7 mm end-diastolic wall thickness and significant 201thallium redistribution after reinjection). The study control group (Group B) consisted of 15 patients with previous myocardial infarction, critical stenosis of LAD and evidence of scarring by imaging techniques (increased echo-reflectivity associated with an end-diastolic wall thickness < 6 mm and no 201thallium redistribution in infarcted areas). The QTc interval was measured at rest and at peak stress in all leads, and particularly in infarct-related leads showing ST-T changes, and the lead-by-lead fractional difference percentage between the QTc intervals (delta QTc) was calculated. The delta QTc was measured again during exercise testing in 11 patients from Group A (Group A1) who showed significant contractility recovery three months after complete myocardial revascularization. A delta QTc shortening < -10% was considered "significant". RESULTS: In 14/15 patients from Group A, a significant delta QTc shortening was measured, while in 14/15 patients from Group B no significant delta QTc shortening was detected (sensitivity = 93.3%; specificity = 93.3%) (p < 0.0001). The mean delta QTc in Group A was -18.1 +/- 8.5%; the mean delta QTc in Group B was -4.2 +/- 7.8% (p < 0.0001). No patient from Group A1 showed a significant delta QTc shortening in Q-wave leads (mean delta QTc group A1 = +6.9 +/- 14.8%). CONCLUSIONS: delta QTc shortening in infarct-related leads during exercise testing is a simple ECG marker of transmural ischemia and, indirectly, of myocardial-viability. This sign is no more evident after myocardial revascularization and may be useful in identifying "hibernating-myocardium".

[Early and late prognosis in acute myocardial infarct. A retrospective study in patients admitted to the coronary care unit in the past 10 years]. / La prognosi precoce e tardiva nell'infarto miocardico acuto. Studio retrospettivo in pazienti ricoverati in unità coronarica negli ultimi 10 anni.

The prognostic evaluation of the patient with an acute myocardial infarction is one of the most interesting unanswered problems. This is both because of its complexity and its implications in terms of secondary prevention. Several clinical studies have emphasized the reliability of the prognostic evaluation based on data collected during the first 24 hours. We therefore evaluated the prognostic relevance of 26 variables measured in the coronary care unit in 1914 patients admitted to our Unit as a result of acute myocardial infarction during the past 10 years. Twenty-four patients were lost to follow-up so that the evaluation refers to 1,890 patients, 1,506 of whom are males aged between 22 and 99 years (mean 58.1) and 384 are females aged between 29 and 88 years (mean 67.1); thus there is a greater prevalence of males. The sex-related difference in the age distribution is statistically significant. In-hospital mortality was analyzed using univariate and multivariate statistical methods (chi-squared test, multiple logistic regression analysis). The prognostic relevance of the considered variables in relation to the survival was analysed using the logrank test and using Cox's model. The variables associated with a greater risk of in-hospital death were found to be: age, presence of diabetes, anterior location of the infarct, arterial hypotension at admission, Killip class III and IV and the presence of ventricular tachyarrhithmias. In contrast, smokers had a lower in-hospital death risk. As to mortality during the follow-up, there was an association with age, female sex, pre-existent coronary disease, presence of high heart rate on admission, low peripheral tissue perfusion, x-ray documented pulmonary congestion, supraventricular tachiarrhythmias and intraventricular block. In contrast, the presence of obesity was associated with a reduced death risk during the follow-up. During the follow-up the most frequent cause of death was re-infarction, followed by sudden death, death from non-cardiac causes and heart failure.

[The Italian Group for the Study of Streptokinase in Myocardial Infarct: Changes in surface cardiac potentials. Study with chest electromaps]. / G.I.S.S.I.: Variazioni dei potenziali cardiaci di superficie. Studio con elettromappe toraciche.

The electrocardiographic changes during and after the thrombolytic treatment with streptokinase (SK) were assessed by means of body surface potential mapping. The aim of the study was to identify potential patterns suggesting reperfusion and revealing possible short-term effects on the infarct size of the recanalization. We studied 23 patients enrolled in the G.I.S.S.I. trial; 11 had an anterior and 12 had an inferior myocardial infarction; 14 were treated with SK and 9 were controls. Body surface maps were recorded from 105 lead points located on the anterior thoracic surface using an automated instrument. The maps were obtained immediately before the SK infusion (or at the time of randomization in the control patients), 30, 60, 120 minutes thereafter and then 24 hours and 7 days after the onset of the infarct symptoms. In each patient the surface potential distribution at 100 msec after the end of QRS was considered and the sum of all the positive potential values was calculated (sigma ST). In addition, the potential time integrals relating to two intervals of the cardiac cycle (first 100 msec of ST and first 40 msec of QRS) were calculated at each lead point and transferred to diagrams representing the chest surface explored (isointegral map). With respect to Q-40 maps, deviation index maps were calculated as follows: the mean Q-40 map (obtained from 30 normal subjects) was subtracted from the map of each patient; the value obtained at each lead point was then divided by the standard deviation of the normal values for that point. An area where the integral values were at least 2 SD lower than normal was considered a reliable index of infarct. By considering as index of reperfusion an early peak of CPK (less than 12 hours from the onset of infarct symptoms), we divided the patients into 2 subsets: reperfused (R) and not reperfused (NR). The mean values of sigma ST at 100 msec progressively decreased in all patients from the baseline to the subsequent recordings in both control and SK groups, without significant differences; nevertheless, the highest percent reductions of sigma ST were observed only in some R patients. The maximum on the ST-100 isointegral maps also showed a similar behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)