Extent Of ST Segment Elevation Research Articles

Morphological identification of brugada type 1 pattern using loop recorder: a feasibility study

Abstract Introduction The presence of spontaneous type 1 Brugada pattern (BP1) is associated with an elevated risk of arrhythmic events. Diagnosis of this condition is often underestimated due to its intermittent nature. While periodic ambulatory ECG monitoring can distinguish patients with pharmacologically induced patterns from those with spontaneous patterns, the diagnostic capabilities of this method are limited. Implantable cardiac monitors (ICM), designed to continuously record heart rhythm, may offer higher sensitivity in detecting patients with intermittent patterns. However, the ICM's ability to morphologically identify the ST segment elevation associated with BP1 remains uncharted. Purpose This study aimed to assess the ICM's capacity to morphologically identify the ST segment elevation associated with BP1. Methods We enrolled all patients who underwent ajmaline testing (AT) between November 2022 and September 2023 in our centre. For positive patients, the external simulator of a loop recorder was utilized to evaluate four positions (I-II left intercostal space at a 45° tilt, II-III left intercostal space at a 45° tilt, II-III right parasternal intercostal space, and II-III left parasternal intercostal space). These positions were selected to capture the trace with the most significant ST segment elevation at the J point during the peak positivity of the ECG during the ajmaline test. Measurements from the recorded traces were acquired using dedicated software. Results Out of 50 patients, 21 (male-to-female ratio 1.62:1, mean age 43.4±13.1 years) had a positive AT result. Seventeen patients exhibited ST segment elevation in the simulator trace during the highest ajmaline dose. Among these patients, the optimal recording position was in the I-II left intercostal space at a 45° tilt in 66.7% of cases. The median ST segment elevation recorded by the simulator was 0.9 mm (interquartile range 0.6-1.1 mm). Notably, there was no observed correlation between the extent of ST segment elevation in the ECG and that recorded by the simulator trace (Pearson linear coefficient = 0.09). Conclusions ICM may offer the potential to record BP1, a finding that holds significant diagnostic and prognostic implications for asymptomatic patients with pharmacologically induced BP1. Further research is needed to develop useful programming algorithms for the automatic recording of this pattern.

Clinical and electrocardiographic characteristics in patients with fulminant myocarditis.

BackgroundThe purpose of this study was to evaluate clinical and electrocardiographic characteristics in patients with fulminant myocarditis.MethodsA total of 72 patients were divided into three groups: pericarditis (control: n = 25), acute myocarditis (n = 27), and fulminant myocarditis (n = 20). Patients' characteristics and electrocardiograms on admission were retrospectively analyzed in the three groups.ResultsBNP levels in the fulminant group were significantly higher than those in the other two groups. ST elevation was observed at lead aVR in the fulminant myocarditis group, whereas ST depression was observed at lead aVR in the other groups (p = .001). The maximum degree of ST elevation among the three groups was similar. However, the number of ST‐elevation leads in the fulminant myocarditis group was significantly lower than that in the other groups (p = .004). The voltage of R wave in lead V5 in the fulminant myocarditis group was significantly lower than that in the other groups (p = .005). Moreover, in the Cabrera sequence, the prevalence of ST elevation in the inferior leads, aVR, and V3–V6 in the fulminant myocarditis group was significantly or nearly significantly lower than that in the other groups.ConclusionsIn fulminant myocarditis, ST‐segment elevation was observed in lead aVR, and contrarily, the number and extent of ST‐segment elevation and R wave voltage were smaller than those in the other groups. These results suggest that the number of myocytes with maintained action potential may be reduced following progressive myocardial damage and interstitial edema due to severe inflammation.

Comparison of Electrocardiographic Characteristics in Men Versus Women ≤ 55 Years With Acute Myocardial Infarction (a Variation in Recovery: Role of Gender on Outcomes of Young Acute Myocardial Infarction Patients Substudy)

Young women with acute myocardial infarction (AMI) have a worse prognosis than their male counterparts. We searched for differences in the electrocardiographic presentation of men and women in a large, contemporary registry of young adults with AMI that could help explain gender differences in outcomes. The qualifying electrocardiogram was blindly assessed by a central core lab in 3,354 patients (67% women) aged 18 to 55 years included in the Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients study. Compared with men, women did not have a different frequency of sinus rhythm, and they had shorter PR and QRS intervals and longer QTc intervals. Intraventricular conduction disturbances were not different among genders. Notably, women were more likely than men to have abnormal Q waves in anterior leads and a lower frequency of Q waves in other territories. ST-segment elevation myocardial infarction (STEMI) diagnosis was less frequent in women than in men (44.6% vs 55.1%, p < 0.001). Among patients with STEMI, women had less magnitude and extent of ST-segment elevation than men. In patients with non-STEMI, the frequency, magnitude, and extent of ST-segment depression were not different among genders, but women had anterior ST-segment depression less frequently and anterior negative T waves more frequently compared with men. These differences remained statistically significant after adjusting for baseline characteristics. In conclusion, there are significant gender differences in the electrocardiographic presentation of AMI among young patients. Further studies are warranted to evaluate their impact on gender-related differences in the management and outcomes of AMI.

Abstract 15688: Electrocardiographic Patterns Differentiating "Apical Ballooning" From Anterior Myocardial Infarction

Introduction: Left ventricular apical ballooning (AB) mimics anterior myocardial infarction (AMI). This study assessed if the ECG can differentiate between these two syndromes with a similar clinical presentation. Methods: Among 2086 patients (pts) with an ACS, 33 (1.6%) with AB were identified (29 f, 4 m, median age 77 years) and compared to 28 consecutive age and sex matched AMI pts undergoing PCI of the LAD with similar findings on LV angiography. Results: AB pts arrived at the hospital later after symptom onset (median 21 vs 5 hours; p&lt;0.001). On the admission ECG, the number of leads with ST-segment elevation (4 [3-6] vs 5 [5-7], p=0.005) and the magnitude of ST-segment elevation (0.7 [0.5-0.9] vs 0.9 [0.7-1.5] mV, p=0.002) were greater in AMI. Reciprocal ST-segment depression was similar (27% vs 54%, p=ns). A positive T wave in aVR was more frequent in AB (49% vs 7%, p&lt;0.001). During follow-up, AB pts had more leads with T-wave inversion (8 [8-9] vs 6 [5-8], p&lt;0.001) and a larger magnitude of T-wave inversion (2.9 [2.2-4.6] vs 1.4 [0.9-2.3] mV, p&lt;0.001). T-wave inversion was similar in I, aVL and V2-V5. AB pts, however, showed negative T-waves also in lead II (74% vs 22%, p&lt;0.001), III (34% vs 4%, p=0.004), aVF (51% vs 11%, p=0.001) and a positive T wave in aVR (100% vs 70%, p=0.005). The QTc interval was longer in AB (515 [482-543] vs 458 [435-484] ms, p&lt;0.001). An abnormal Q wave on admission was more frequent in AMI (21% vs 79%, p&lt;0.001) and persisted but was absent in AB at discharge (0% vs 61%, p&lt;0.001). Ventricular tachycardia was similar (2% vs 14%, p=ns) but atrial fibrillation occurred only in AB (21% vs 0%, p=0.013). The ECG normalized in all AB but in only 1 AMI pt (p&lt;0.001). Overall, despite a similar ejection fraction (54±15 vs 55±13 %) and lower troponin I values (7.5±6.9 vs 238±221 ng/ml, p&lt;0.001), AB pts developed significantly more adverse events compared to AMI pts (52% vs 18%, p&lt;0.008). Conclusion: ECG patterns in AB are significantly different from those in AMI. On admission, the extent of ST-segment elevation and the number of Q waves are greater in AMI. During follow-up, no Q wave, a longer QTc interval, a greater extent of T-wave inversion and a positive T wave in aVR are typical findings in AB. Adverse events are more frequent in AB than in AMI.

Clinical relevance of angiographic coronary collaterals during primary coronary intervention for acute ST-elevation myocardial infarction

Background Collaterals to occluded infarct-related coronary arteries (IRA) have been observed after the onset of acute ST-elevation myocardial infarction (STEMI). We sought to investigate the impact of early coronary collateralization, as evidenced by angiography, on myocardial reperfusion and outcomes after primary percutaneous coronary intervention (PCI). Methods Acute procedural results, ST-segment resolution (STR), enzymatic infarct size, echocardiographic left ventricular function, and major adverse cardiac events (MACE) at 6-month follow-up were assessed in 389 patients with STEMI undergoing primary PCI for occluded IRA (TIMI flow grade 0 or 1) within 12 hours of symptom-onset. Angiographic coronary collateralization to the occluded IRA at first contrast injection was graded according to the Rentrop scoring system. Results Low (Rentrop score of 0 or 1) and high (Rentrop score of 2 or 3) coronary collateralization was detected in 329 and 60 patients, respectively. Patients with high collateralization more commonly had prior stable angina and right coronary artery occlusion, but less often had left anterior descending artery occlusion. At baseline, these patients presented with less extent of ST-segment elevation and lower serum levels of creatine kinase myocardial band (CK-MB) and cardiac troponin I (cTnI). Procedural success rate, STR, corrected TIMI flame count, and area under the curve of CKMB and cTnI measurements after the procedure were similar between patients with high collateralization and those with low collateralization (for all comparisons P&gt;0.05). There were no differences in left ventricular ejection fraction and rates of MACE at 6 months according to baseline angiographic collaterals to occluded IRA. Conclusions In patients with acute STEMI undergoing primary PCI within 12 hours of symptom-onset, coronary collateralization to the occluded IRA was influenced by clinical and angiographic features. Early recruitment of collaterals limits infarct size at baseline, but has no significant impact on myocardial reperfusion after the procedure and subsequent left ventricular function and clinical outcomes.

Prevalence and non-invasive predictors of left main or three-vessel coronary disease: evidence from a collaborative international meta-analysis including 22 740 patients

BackgroundLeft main disease (LMD) and three-vessel disease (3VD) have important prognostic value in patients with coronary artery disease. However, uncertainties still exist about their prevalence and predictors in patients with...

CIRCUMFLEX ARTERY RELATED MYOCARDIAL INFARCTION: LESS REPERFUSION THERAPY AND LARGE INFARCT SIZE

Whether or not reperfusion therapy is initiated is often based on the extent of ST segment elevation on the 12 lead admission ECG. However, an occlusion of the circumflex (CX) coronary artery often present without ST segment elevation. In an all comer acute coronary syndromes (ACS) population, we

ST-Segment Recovery and Outcome After Primary Percutaneous Coronary Intervention for ST-Elevation Myocardial Infarction

Primary percutaneous coronary angioplasty is an effective and widely adopted treatment for acute myocardial infarction. A simple method of determining prognosis after primary percutaneous coronary intervention (PCI) would facilitate appropriate care and expedite hospital discharge. Thus, we determined the prognostic importance of various measures of ST-segment-elevation recovery after primary PCI in a large, contemporary cohort of patients with ST-elevation myocardial infarction. We analyzed ECG data describing the magnitude and extent of ST-segment elevation and deviation before and early after (ie, 30 minutes) primary PCI in the study cohort of 4866 subjects with electrocardiographically high-risk ST-elevation myocardial infarction enrolled in the Assessment of PEXelizumab in Acute Myocardial Infarction (APEX-AMI) trial. Associations among 6 methods for calculating ST-segment recovery, biomarker estimates of infarct size (ie, peak creatine kinase, creatine kinase-MB, and troponin I and T), and prespecified clinical outcomes (ie, rates of 90-day death and 90-day death, heart failure, or shock) were examined. All ST-segment-recovery methods provided strong prognostic information regarding clinical outcomes. A simple ST-segment-recovery method of residual ST-segment elevation measurement in the most affected lead on the post-PCI ECG performed as well as complex methods that required comparison of pre- and post-PCI ECGs or calculation of summed ST-segment deviation in multiple leads (ie, worst-lead residual ST elevation: adjusted hazard ratio for 90-day death rate [reference <1 mm]: 1 to <2 mm, 1.23 [95% CI 0.74 to 2.03]; > or =2 mm, 2.22 [95% CI 1.35 to 3.65], corrected c-index=0.832; 90-day death/congestive heart failure/shock [reference <1 mm]: 1 to <2 mm, 1.55 [95% CI 1.06 to 2.26]; > or =2 mm, 2.33 [95% CI 1.59 to 3.41], corrected c-index=0.802). Biomarker estimates of infarct size declined in association with enhanced ST-segment recovery. An ECG performed early after primary PCI is a simple, widely available, inexpensive, and powerful prognostic tool applicable to patients with ST-elevation myocardial infarction.

EKG-Veränderungen beim akuten Koronarsyndrom: „Apical ballooning” versus Vorderwandinfarkt

Transient left ventricular (LV) apical ballooning (AB) is characterized by chest pain, electrocardiographic (ECG) changes and LV apical akinesia mimicking anterior myocardial infarction (AMI) in the absence of coronary artery disease. This study aimed to assess if the ECG could reliably differentiate between these two syndromes with a similar clinical presentation. Among 2086 patients with an acute coronary syndrome (ACS) undergoing coronary angiography over a 6.5-year period, 33 patients (1.6 %) with apical ballooning (AB) were identified (29 f, 4 m, median age 77 [68 - 80] years). AB patients were compared to 28 consecutive age and sex matched AMI patients (23 f, 5 m; 68 [56 - 76] years) undergoing successful PCI of the LAD with similar findings on LV angiography. We compared the ECG on admission, at the time of maximal T-wave inversion, before discharge and the longest QTc-interval. The number of leads showing ST-segment elevation (4 [3 - 6] vs. 5 [5 - 7]; p = 0,005) and the sum of the level of ST-segment elevation (0,7 [0,5 - 0,9] mV vs. 0,9 [0,7 - 1,5] mV; p = 0,002) was significantly greater in AMI. An abnormal Q wave at presentation was more frequent in AMI (21 % vs 79 %, p < 0.001) and persisted in half of AMI patients whereas the Q wave disappeared in all AB patients during follow-up (0 % vs. 61 %, p < 0.001). The QTc interval was significantly longer in AB (568 [521 - 614] ms vs. 471 [438 - 513] ms; p < 0,001). During follow-up, AB patients displayed significantly more leads with T-wave inversion (8 [8 - 9] vs. 6 [5 - 8]; p < 0,001), and the sum of the level of T-wave inversion (2,9 [2,2 - 4,6] mV vs. 1,4 [0,9 - 2,3] mV; p < 0,001) was significantly larger than in AMI. A formula considering ST-segment elevation on admission and T-wave inversion as well as Q waves during follow-up allowed discrimination between AB and AMI (sensitivity 93 %, specificity 86 %). ECG findings in AB patients are significantly different from those in AMI patients. At initial presentation, the extent of ST-segment elevation and the number of abnormal Q waves are greater in AMI. During follow-up, no Q wave, a longer QTc interval and a greater extent of T-wave inversion are typical findings in AB patients.

Grade 3 ischemia on admission and absence of prior beta-blockade predict failure of ST resolution following thrombolysis for anterior myocardial infarction

Background ST segment resolution (STR) is a strong predictor of outcome following thrombolysis. If failure of STR could be predicted on admission, better selection of treatment may be possible. Among patients given reperfusion, those with terminal QRS distortion (grade 3 ischemia) have larger infarcts, but the mechanism underlying this association is unclear. Whether grade 3 ischemia on admission can predict STR is unknown. Methods We studied 180 consecutive patients given thrombolysis for a first anterior acute myocardial infarction (AMI). Multiple variables available on admission were analyzed as predictors of STR at 1, 2, and 24 h and as predictors of the need for rescue percutaneous coronary intervention (PCI). Results Multivariate predictors of failure of STR were: for 1 h: extent of ST elevation (OR: 1.09 [1.01–1.18]); for 2 h: no previous use of beta-blockers (OR: 4.71 [1.56–13.98]) and grade 3 ischemia (OR: 6.77 [3.27–13.95]); for 24 h: previous use of aspirin (OR: 6.70 [1.31–34.01]) and grade 3 ischemia (OR: 29.44 [7.30–118.1]). Grade 3 ischemia had a strong positive predictive value for failure of STR at 1 and 2 h and was the strongest predictor of the need for rescue PCI. Conclusions Grade 3 ischemia on admission is the strongest independent predictor of failure to achieve myocardial reperfusion after thrombolysis. This association may underlie the larger infarcts associated with grade 3 ischemia. Other predictors of reperfusion failure are the extent of ST segment elevation, prior use of aspirin and no prior use of beta-blockers.

Effect of time interval between two balloon inflations on ischemic preconditioning during coronary angioplasty

Ischemic preconditioning, defined as a reduction in myocardial ischemia caused by repeated brief episodes of coronary occlusions, is observed during percutaneous transluminal balloon angioplasty (PTCA). To elucidate the effects of the length of the interval between consecutive balloon inflations on ischemic preconditioning during PTCA, we examined 62 patients with chronic stable angina (48 males and 14 females; mean age 62 ± 10 yr). PTCA was performed on the left anterior descending artery lacking in collateral vessels. A 2-min balloon inflation was performed twice and the extent of ST segment elevation in the electrocardiogram and the severity of chest pain (scored from 0 to 10) for each inflation were determined and compared. Patients were divided into three groups according to the interval between the two inflations: 1 min, Group 1; 2 min, Group 2; and 5 min, Group 5. In Groups 2 and 5, ST-segment elevation was significantly decreased during the second balloon inflation, as compared with that during the first inflation (P < 0.01, P < 0.001). A significant decrease was also observed in the severity of chest pain (P < 0.05, P < 0.01). However, Group 1 showed no significant decrease in ST-segment elevation or severity of chest pain between the first and second inflations. ST-segment elevation and chest pain were reduced to a greater extent in Group 5 than in Group 2. Results suggest that an interval of more than 2 min between balloon inflations is required to achieve ischemic preconditioning during PTCA. Cathet. Cardiovasc. Diagn. 42:263–267, 1997. © 1997 Wiley-Liss, Inc.

Effect of time interval between two balloon inflations on ischemic preconditioning during coronary angioplasty.

Ischemic preconditioning, defined as a reduction in myocardial ischemia caused by repeated brief episodes of coronary occlusions, is observed during percutaneous transluminal balloon angioplasty (PTCA). To elucidate the effects of the length of the interval between consecutive balloon inflations on ischemic preconditioning during PTCA, we examined 62 patients with chronic stable angina (48 males and 14 females; mean age 62 +/- 10 yr). PTCA was performed on the left anterior descending artery lacking in collateral vessels. A 2-min balloon inflation was performed twice and the extent of ST segment elevation in the electrocardiogram and the severity of chest pain (scored from 0 to 10) for each inflation were determined and compared. Patients were divided into three groups according to the interval between the two inflations: 1 min, Group 1; 2 min, Group 2; and 5 min, Group 5. In Groups 2 and 5, ST-segment elevation was significantly decreased during the second balloon inflation, as compared with that during the first inflation (P < 0.01, P < 0.001). A significant decrease was also observed in the severity of chest pain (P < 0.05, P < 0.01). However, Group 1 showed no significant decrease in ST-segment elevation or severity of chest pain between the first and second inflations. ST-segment elevation and chest pain were reduced to a greater extent in Group 5 than in Group 2. Results suggest that an interval of more than 2 min between balloon inflations is required to achieve ischemic preconditioning during PTCA.

Fate of Collateral Vessels After Successful Coronary Angioplasty in Patients With Effort Angina

Objectives. The purpose of the present study was to evaluate whether severe restenosis after percutaneous transluminal coronary angioplasty (PTCA) promotes collateral development and whether successful dilation regresses collateral vessels.Background. It is well known that in the presence of severe coronary stenosis, native collateral arterioles mature to small coronary arteries with several layers of smooth muscle cells. However, it remains unclear whether well developed collateral vessels regress after removal of coronary stenosis.Methods. The study group comprised 41 patients who underwent elective PTCA for effort angina due to single-vessel disease, followed by repeat PTCA to treat restenosis. We classified the patients into three groups depending on the change in baseline Thrombolysis in Myocardial Infarction (TIMI) flow grade of the ischemia-related artery at initial and repeat PTCA, and we compared the extent of ST segment elevation at 1 min of the first balloon inflation between the two procedures. The average interval from initial to repeat PTCA was 125 days.Results. The three patient groups comprised group A, 12 patients with decreased flow grade because of severe coronary restenosis; group B, 12 patients with increased flow grade who had severe initial stenosis and relatively mild restenosis; and group C, 17 patients with unchanged flow grade. In the presence of comparable rate-pressure products at initial and repeat PTCA, patients in group A had significantly greater ST segment elevation (p < 0.01) at initial than at repeat PTCA (mean ± SD 0.42 ± 0.31 vs. 0.13 ± 0.22 mV). In group B, ST segment elevation was significantly less at initial than at repeat PTCA (0.13 ± 0.25 vs. 0.19 ± 0.17 mV, p < 0.05), and in group C, it was comparable at the two procedures (0.37 ± 0.32 vs. 0.35 ± 0.33 mV, p = 0.50).Conclusions. These findings indicate that severe restenosis after PTCA promotes collateral development and that successful dilation regresses collateral vessels during a relatively short period of time.(J Am Coll Cardiol 1997;29:544–8)

Efficacy of amoldipine besilate therapy for variant angina: Evaluation by 24-hour Holter monitoring

The efficacy of amlodipine, a calcium antagonist, was investigated in 12 patients with variant angina. Amlodipine was administered at a dose of 5 mg once daily, and efficacy was assessed from the frequency of anginal attacks, the frequency of ST elevation or depression, and the extent of ST segment changes [ST segment elevation or depression (mm) x duration (seconds)] on the Holter ECG before and after treatment. The frequency of ST elevation during the observation period was 1.67 +/- 0.33 times/day (symptomatic attacks: 1.17 +/- 0.21/day; asymptomatic attacks: 0.50 +/- 0.19/day), and this significantly decreased to zero per day (both symptomatic and asymptomatic attacks) after treatment (p < 0.05). The extent of ST segment elevation during the observation period was 507.5 +/- 156.6 mm.sec/day (symptomatic: 382.5 +/- 102.9 mm.sec/day; asymptomatic: 125.0 +/- 62.0 mm.sec/day), and such changes were completely suppressed (both symptomatic and asymptomatic) by treatment (p < 0.05). The frequency of ST depression was 2.08 +/- 0.42 times/day (symptomatic: 0.25 +/- 0.13/day; asymptomatic: 1.83 +/- 0.37/day) during the observation period, while it was 1.50 +/- 0.36 times/day (symptomatic: 0.25 +/- 0.13/day; asymptomatic: 1.25 +/- 0.30/day) after treatment. Although anginal attacks remained unchanged, asymptomatic attacks tended to decrease (p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of ATP-sensitive K+ channel on ECG ST segment elevation during a bout of myocardial ischemia. A study on epicardial mapping in dogs.

ATP-sensitive K+ channels are activated when the myocardium becomes ischemic. However, the role of the ATP-sensitive K+ current in the emergence of ECG ST changes during ischemia remained unclarified. The left anterior descending coronary artery (LAD) was cannulated and perfused with arterial blood from the carotid artery through a bypass tube in 8 anesthetized, open-chest dogs. An array of 60 unipolar electrodes mounted on a sock was used to record epicardial electrograms of the whole heart. Pinacidil (10 micrograms.kg-1 x min-1), an ATP-sensitive K+ channel opener, was infused into the bypass tube for 2 minutes, and the electrograms were recorded before and after the infusion. The elevation of the ST segment and the increase of QRST area were observed spatially over the LAD-perfused region. At the electrode showing the largest ST segment elevation, the activation recovery interval, an index of action potential duration, was shortened from 202 +/- 9 to 111 +/- 18 milliseconds (P < .001). These electrographic changes were similar to those noted in 2-minute coronary occlusion (n = 8). The extent of ST segment elevation during coronary occlusion was attenuated after the intravenous pretreatment with glibenclamide (0.3 mg/kg), a blocker of the KATP channel (n = 5). The findings of this study suggest that the activation of ATP-sensitive K+ channels during a bout of acute myocardial ischemia plays an important role in the emergence of ECG ST elevation.

Reduction in reperfusion injury by blood-free reperfusion after experimental myocardial infarction

Because myocardial reperfusion injury may be caused by various blood constituents, a transient period of blood-free reperfusion was evaluated in closed chest dogs subjected to a 90 min angioplasty balloon occlusion of the left anterior descending coronary artery. In the treated group (n = 13), the balloon remained inflated for an additional 15 min while the infarct vessel was perfused with an acellular oxygenated perfluorochemical emulsion (Fluosol). The balloon was then deflated, permitting blood reperfusion. In the control group (n = 13), the balloon was deflated after 90 min of coronary occlusion. One week after infarction, the area at risk was defined in vivo by monastral blue dye staining, and the area of myocardial necrosis was assessed using triphenyltetrazolium chloride staining with histologic confirmation. Major determinants of infarct size, including rate-pressure product, area at risk and severity of myocardial ischemia (assessed by the extent of ST segment elevation during coronary occlusion), were not significantly different in the two groups. Treated dogs demonstrated a 47% reduction in infarct size expressed as a percent of the area at risk compared with control dogs (27.0 +/- 4.4% versus 50.8 +/- 4.4%, p less than 0.01). Treated dogs also demonstrated a superior global left ventricular ejection fraction (57.5 +/- 2.5% versus 51.0 +/- 2.2%, p less than 0.05) and anterolateral (regional) ejection fraction (32.6 +/- 3.6% versus 19.8 +/- 3.9%, p less than 0.05) compared with values in control dogs assessed by contrast ventriculography after 1 week of reperfusion. It is concluded that a transient period of blood-free reperfusion with an oxygenated perfluorochemical reduces reperfusion injury in a canine model of myocardial infarction.

Reciprocal ST Segment Changes in Acute Myocardial Infarction; Informative or Incidental?

The majority of patients show elevation of the ST segment of the surface electrocardiogram during the acute phase of transmural myocardial infarction. In a significant proportion of such patients, depression of the ST segment is observed in an area of myocardium away from the infarcted territory. In spite of the recognition of this reciprocal ST segment depression for some decades, its aetiology and diagnostic and prognostic significance have been elusive and the subject of controversy. There is general, but not uniform, agreement that patients showing reciprocal ST segment depression usually have more extensive myocardial damage than those without reciprocal changes. Assessments have included echocardiography [1], radionuclide ventriculography for ejection fraction and wall motion abnormalities [2, 3], thallium perfusion scintigraphy [4], enzyme release [2, 5] and in-hospital complications including heart failure and dysrhythmias [6]. It is logical to assume that the longer-term prognosis of such patients is somewhat less good, although evidence is limited and based on series too small to provide reliable prognostic information [7, 8]. Two general views have been advanced to explain reciprocal ST segment changes in acute myocardial infarction. The first contends that ST segment depression in areas presumably remote from the infarct territory is an electrical phenomenon related to the extent of ST segment elevation over the infarct territory. The second contends that ischaemia 'at a distance' underlies the ST segment depression, related to compromise of myocardial perfusion either from the same or a different artery to that supplying the infarct territory. It is likely that neither view is exclusively correct because of time-related changes in currents of injury after myocardial infarction. Thus, it was shown over 25 years ago in a canine model that ST segment elevation from the anterior epicardial electrogram after left anterior descending coronary artery ligation was associated immediately with ST segment depression on the epicardial surface of the posterior wall, directly opposite the evolving infarct [9]. Within 20 min, however electrodes on the periphery of the infarct that had recorded ST segment elevation initially showed ST segment depression as a marker of local myocardial injury. Clearly, the 12 lead body surface electrocardiogram is insufficient to differentiate reliably between such non-infarct and peri-infarct phenomena. Transient reciprocal ST segment changes, for example during coronary angioplasty [10,11], do not necessarily reflect currents of injury during evolving myocardial infarction. Protagonists of these two viewpoints have examined the predictive value of reciprocal ST

Normalization of Abnormal T Waves in Ischemia

Inverted T waves due to coronary artery disease and previous myocardial infarction were observed to revert ot normal, upright position during ischemia in 38 patients. The normalization of inverted T waves was seen on the electroencephalograms of 19 patients during spontaneously occurring angina pectoris and of 11 patients when ischemia was provoked by treadmill exercise; for 8 patients, normalization occurred during the administration of isoproterenol hydrochloride and during the consequent episode of angina pectoris. The mechanism for normalization may be the algebraic sum of the extent of ST segment elevation and the amplitude of the T waves of acute ischemia plus the extent of preexisting ST segment depression and the degree of T wave inversion, to result in isoelectric ST segment and upright T wave. As with myocardial infarction, reciprocal changes may also be recorded. However, the reciprocal nature may be masked since either acute ST segment elevation of T wave inversion, or both, may not be recorded in the leads reflecting the ischemic area because of normalization.