Impact of infarct artery patency on the relationship between electrocardiographic and ventriculographic evidence of acute myocardial ischaemia.

Routine invasive evaluations are being abandoned, and thus simple non-invasive methods for estimating the extent of jeopardized myocardium during evolving myocardial infarction are needed for risk stratification to guide the appropriate therapeutic intervention. With this in mind the aim of the paper was to evaluate the association between ischaemic changes in the standard electrocardiogram and the function of acutely infarcted myocardium in relation to infarct artery patency status. Forty consecutive patients with a first acute myocardial infarction, admitted within 6 h of symptom onset and without bundle branch or fascicular block were included. Summated ST segment elevation in 11 electrocardiographic leads (aVR excluded) was measured to the nearest 0.05 mV and compared to regional wall motion, estimated by the centreline method (SD/chord) and global left ventricular ejection fraction (% LVEF) after thrombolytic therapy. Acute angiographic and ST segment measurements were performed at a median 254 min (range 70-485) after the onset of symptoms. Patients were grouped according to infarct artery patency status after intravenous thrombolysis. Of the 40 patients, 27 had a patent (Thrombolysis In Acute Myocardial Infarction trial (TIMI) grade 2-3 flow) and 13 had persistently occluded (TIMI 0-1 flow) infarct arteries. Anterior myocardial infarction was present in 13 and seven patients in the two groups. In the TIMI 2-3 group, the summated ST elevation did not correlate with % LVEF or SD/chord (rs = -0.08; and rs = -0.17, respectively). In the TIMI0-1 group the summated ST elevation correlated inversely with both % LVEF and SD/chord (rs = -0.70; and rs = -0.56, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of early and complete reperfusion to achieve myocardial salvage after thrombolysis in acute myocardial infarction.

The importance of the timing and completeness of coronary artery reperfusion for limitation of acute myocardial infarction (AMI) size after intravenous thrombolytic therapy was studied in 39 patients. All had electrocardiographic epicardial injury and acute coronary angiography performed < 8 hours after symptom onset. Acutely jeopardized myocardium was estimated at baseline, and before and after angiography by quantitative ST-segment analysis. The AMI size was estimated on the final electrocardiogram by the Selvester QRS score. Left ventricular ejection fraction was measured at the time of acute angiography and before discharge in 31 of these patients. In the 21 patients with normal flow (Thrombolysis in Myocardial Infarction [TIMI] trial grade 3) in the infarct-related artery, the amount of jeopardized myocardium decreased from baseline to that before and after angiography (17 to 11 and 11%, respectively; p < 0.00005), and the median final AMI size was reduced (17 to 9%; p = 0.0004). In 6 patients with suboptimal flow (TIMI grade 2), the median amount of jeopardized myocardium decreased slightly from baseline to that before to after angiography (15 to 12%); however, the median final AMI size was not reduced (17%). In 12 patients with no reperfusion (TIMI 0 to 1) flow, the median amount of jeopardized myocardium remained unchanged from baseline to that before angiography (21%), and the final AMI size was not significantly reduced. There was a significant inverse correlation between the change in global left ventricular function and the difference between electrocardiographic estimated jeopardized and final AMI size (rs = -0.53; p = 0.008).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of the 12-lead ECG to detect myocardial reperfusion and salvage during acute myocardial infarction.

In this era of thrombolytic therapy, the standard 12-lead electrocardiogram (ECG) is easily available and noninvasive and could provide indicators of myocardial reperfusion and salvage. Previous reports have proposed that a decrease of total ST-segment elevation of > or = 20% from the pre- to the immediate posttreatment ECG is indicative of reperfusion, and that a > or = 20% decrease from the initial infarct size predicted by ST-segment deviation on the admission ECG to the final infarct size estimated by QRS score on the predischarge recording is indicative of myocardial salvage. This prospective study of 29 patients with myocardial infarction and angiographically documented reperfusion shows that the > or = 20% threshold for ST resolution achieved 79% sensitivity and 70% specificity in patients receiving intravenous therapy and 90% sensitivity in those receiving rescue intracoronary therapy. However, it should be noted that 21% of patients with successful intravenous therapy failed to achieve even this threshold of ST resolution. Regarding myocardial salvage, 63% of patients receiving intravenous and 90% of those receiving rescue intracoronary therapy achieved the threshold of > or = 20% decrease in infarct size.

Correlation of the complete version of the Selvester QRS scoring system with quantitative anatomic findings for multiple left ventricular myocardial infarcts.

The correlation between myocardial infarct size estimated by the complete version of the Selvester QRS scoring system and that documented by pathoanatomic studies has been reported for single anterior, inferior and posterolateral infarcts. Although previous studies described electrocardiographic changes in patients with multiple infarcts, no quantitative documentation of the ability of such changes to estimate the total amount of left ventricular infarction has been reported. This study of 32 patients with anatomically documented multiple infarcts shows a significant correlation between QRS-estimated and anatomically documented sizes (r = 0.44; p = 0.01), which is less than that previously reported for single infarcts in the anterior, inferior and posterolateral locations. Several of the 54 electrocardiographic criteria were never satisfied. Criteria for posterior infarction were seldom present, suggesting "cancellation effect" of coexisting anterior infarction. These results will be the basis for future modification of QRS criteria for estimating myocardial infarct size.

Evaluation of changes in standard electrocardiographic QRS waveforms recorded from activity-compatible proximal limb lead positions.

Proximal limb lead positions are currently used for activity-compatible electrocardiographic monitoring of myocardial ischemia. Two previously described systems for alternate limb lead placement were studied in patients with and without QRS evidence of healed anterior or inferior myocardial infarction. An innovative method was used to simultaneously record 6 standard and 6 modified limb leads, and 3 standard and 3 modified precordial leads on a standard digital electrocardiograph. Both alternate lead placement systems showed rightward frontal plane axis shift and diminished Q-wave durations in lead aVF compared with those of their simultaneous standard controls. Furthermore, potential differences between the standard distal limb lead sites and 5 more proximal sites were explored along each limb. Differences along the left arm were accentuated relative to those along the right arm owing to differences in proximity of the arms to the myocardium. Along the lower limb, and anterior site showed less deviation from standard than did a more lateral site. It is imperative that recordings from alternate sites be labeled accordingly so that their output cannot be confused with that obtained from standard sites.

Indices of reperfusion in patients with acute myocardial infarction using characteristics of the CK-MB time-activity curve.

The purpose of this study was to identify indices of coronary artery reperfusion in patients treated with thrombolytic therapy for acute myocardial infarction (AMI) by means of characteristics from the serum creatine kinase (CK) isoenzyme MB time-activity curve. Frequent blood sampling as performed in three groups with a first AMI: 29 patients treated with intravenous thrombolytic therapy who had a patent infarct-related artery with normal flow (TIMI-3) at acute catheterization (reperfusion group); four patients with a persistently closed infarct-related artery (no reperfusion group); and 44 patients who did not receive any therapy aimed at coronary reperfusion (no thrombolytic therapy group). In the latter group we prospectively estimated that 25% would have spontaneous reperfusion. A physiologically based computer-calculated multi-compartment method was used to determine the characteristics of the serum CK-MB time-activity curve. In addition to demonstrating an earlier increase, a shorter time to peak of serum CK-MB and a lower estimated infarct size in the reperfusion group (p = 0.025 to 0.00001), the appearance rate constant (k1) and time from estimated initial increase to peak of CK-MB in the blood stream (tRP) were significantly different from those values in the no thrombolytic therapy group (p less than 00001). A cutoff level indicating reperfusion if k1 was greater than 0.185 or tRP was less than 16.5 hours demonstrated overlapping values between these two groups in only four patients (k1), two patients (tRP), and six patients with a combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in standard electrocardiographic ST-segment elevation predictive of successful reperfusion in acute myocardial infarction.

The ability of the electrocardiographic ST segment to predict successful reperfusion after thrombolytic therapy remains controversial. To evaluate whether angiographically determined reperfusion could be predicted from changes in ST-segment elevation, the sum of ST-segment elevation in affected leads of the electrocardiogram was compared before and after thrombolytic therapy in 53 patients with acute myocardial infarction (AMI). Reperfusion status of the infarct-related artery was determined angiographically less than 8 hours from onset of symptoms. According to the Thrombolysis in Myocardial Infarction trial (TIMI) criteria, 33 patients had successful reperfusion (TIMI grade 2 to 3 flow) after thrombolytic therapy and 20 patients did not (TIMI grade 0 to 1 flow). Logistic multiple regression analysis showed that the proportional value for the shift in the sum of ST elevation, termed the "% ST change," was more strongly associated with reperfusion than the absolute measured difference in millimeters (chi-square = 11.34 vs 9.22). The entire spectra of sensitivities and specificities were determined to identify a level of the percent ST change with simultaneous high sensitivity and specificity. A 20% decrease in ST elevation provided such a level (88% sensitivity, 80% specificity). The positive and negative predictive values of a 20% decrease in ST elevation were 88 and 80%, respectively. These results suggest that a decrease of only 20% in the sum of ST elevation in the standard electrocardiogram after thrombolytic therapy is a useful noninvasive predictor of reperfusion status in patients with evolving AMI.

Sensitivity of a set of myocardial infarction screening criteria in patients with anatomically documented single and multiple infarcts.

A subset of 3 screening criteria (Q wave greater than or equal to 30 ms in lead aVF, any Q or R wave less than or equal to 10 ms and less than or equal to 0.1 mV in lead V2, and R wave greater than or equal to 40 ms in V1) has been proposed to identify single nonacute myocardial infarcts. Cumulatively, these 3 criteria achieved 95% specificity, and 84 and 77% sensitivities for inferior and anterior myocardial infarcts, respectively, among patients identified by coronary angiography and left ventriculography. This study establishes the true sensitivities of the set of screening criteria in 71 patients with anatomically proven single myocardial infarcts and 32 patients with multiple myocardial infarcts. In the single inferior infarct group, the aVF criterion was 90% sensitive. The V2 criterion (any Q or R wave less than or equal to 10 ms and less than or equal to 0.1 mV) was 67% sensitive in the single anterior infarct group. No single criterion proved sensitive in identifying a posterolateral infarct. The set of screening criteria performed just as well for multiple infarcts as it did for single infarcts, with a cumulative sensitivity of 72%. The overall sensitivity of the screening set in the 103 patients in all groups was 71%.

Anatomic validation of electrocardiographic estimation of the size of acute or healed myocardial infarcts.

Seventeen new criteria added to the simplified version of the Selvester QRS scoring system to comprise the complete version were evaluated to determine their value in estimating the size of single infarcts. These non-Q-wave criteria might be particularly useful regarding posterolateral infarcts in the distribution of the left circumflex artery. The study population was made up of 21 anterior, 30 inferior and 20 posterolateral single myocardial infarction (MI) patients with no evidences of bundle branch or fascicular blocks, ventricular hypertrophy or previous MI on their final stable electrocardiogram. The complete system's maximum 32 points is capable of indicating MI in 96% of the left ventricle and it estimated a mean electrocardiographic MI size that better approximated the anatomic size compared with the simplified version in all MI locations. The correlation between anatomic and electrocardiographic MI size using the complete system was better and statistically significant for the posterolateral MI group (simplified r = 0.55, p less than 0.01 vs complete r = 0.70, p less than 0.0006). Criteria such as Q and S amplitude less than or equal to 0.3 mV in V1 and less than or equal to 0.4 mV in V2 were particularly helpful. This study documents the improved ability provided by the 17 additional non-Q-wave criteria which have been added in the complete version of this scoring system regarding the sizing of infarcts in the region of the left ventricle supplied by the left circumflex artery.

Transient alterations of the QRS complex and ST segment during percutaneous transluminal balloon angioplasty of the right and left circumflex coronary arteries.

The dynamic QRS amplitude changes that appear during 1-vessel percutaneous transluminal coronary angioplasty of the right and left circumflex coronary arteries were studied in 20 patients using continuous 3-lead electrocardiographic recordings representing leads aVF, V2 and V5. The balloon inflations that produced the greatest extent of ST-segment deviation were identified for each lead ("maximally ischemic periods"). QRS amplitude measurements were performed manually at both the PR and shifted J-ST baselines at 10-second intervals during these periods to determine that baseline from which the R and S waves most nearly maintained their control amplitudes. There was no significant baseline relation for either the R or the S waves in leads V2 and V5 during ischemia. However, the R-wave changes in lead aVF were significantly associated with the PR- versus the J-ST-segment baseline (p = 0.007); the S wave, when it occurred, had no tendency for either baseline. The electrocardiographic records were also examined visually for characteristics of left posterior (inferior) "periischemic block" likely to occur uniquely in patients with a dominant right or left circumflex occlusion. There were 2 patients with obstruction of the right circumflex artery who exhibited the characteristics of periischemic block during percutaneous transluminal coronary angioplasty, as evidenced by an increase in R-wave duration, amplitude or both in lead aVF.

Invalidation of the resting electrocardiogram obtained via exercise electrode sites as a standard 12-lead recording.

The difficulty in interpreting the standard 12-lead electrocardiogram (ECG) due to the interference from muscle potentials produced by arm and leg motion makes it unsuitable during the exercise treadmill test. Likewise, the exercise lead placement ECG cannot substitute for the standard ECG due to significant errors in the former's diagnostic interpretation. This study compares the ECGs recorded via standard and exercise sites regarding frontal and horizontal plane axes, diagnosis and location of myocardial infarction and estimation of infarct size using the complete 54-criteria and 32-point Selvester QRS scoring system. The altered limb lead locations on the exercise ECG caused the QRS vectors to artifactually appear to be directed more inferiorly, posteriorly and rightward, producing a marked rightward mean frontal plane axis shift of +48 degrees (p less than 0.00001). No false positive or false negative anterior infarct was seen on the exercise lead placement ECG, whereas inferior and posterior infarcts were lost in 69% and 31% of patients, respectively. A false lateral infarct was seen in 19% of patients. Estimation of infarct size differed between the 2 ECG sets, with 11 patients increasing their infarct size by 3 to 9% and 14 others decreasing it by 3 to 15% on the exercise lead placement ECG. This study demonstrates that use of body torso positions for limb leads results in substantial QRS waveform variations that disqualify the exercise lead placement ECG as a "standard" recording. Such ECGs should therefore be labeled as "torso positioned" or "nonstandard" to prevent misuse for clinical and investigative purposes.

Transient alterations of the QRS complex and ST segment during percutaneous transluminal balloon angioplasty of the left anterior descending coronary artery.

Using continuous 3-lead electrocardiographic (ECG) recordings in 19 patients undergoing elective percutaneous transluminal coronary artery angioplasty (PTCA) of the left anterior descending (LAD) artery, this study described the dynamic changes of the ST segment and the R- and S-wave amplitudes that occur during transient myocardial ischemia. The waveforms from lead V2 were quantified at 10-second intervals during the length of the balloon inflation that produced the greatest extent of ST-segment deviation. The simultaneous changes that occurred in leads aVF and V5 were also observed, but not quantified. Measurements of R- and S-wave amplitudes were performed during maximal ischemia from both the PR- and the J-ST-segment baselines to determine which of these most nearly maintained its control position during ischemia. The results indicate that the R-wave amplitude is best determined from the PR-segment baseline (p = 0.0007), while the S wave is best determined from the J-ST-segment baseline (p = 0.03). However, only a portion of the QRS changes observed during PTCA could be accounted for by the baseline shift. There were additional QRS changes during ischemia in 11 of the patients (58%) suggestive of conduction disturbances in 3 endocardial sites: left septal, right septal and left anterosuperior. It is hypothesized that these changes may represent ischemia-induced delay in conduction ("periischemic block") previously thought to occur only with myocardial infarction.