QRS changes during percutaneous transluminal coronary angioplasty and their possible mechanisms

Genesis of ischemic ST segment changes: A study using precordial bipolar leads and regional vectorcardiograms

BACKGROUND

Precordial Bipolar Leads (PBLs), Weighted Unipolar Leads (WUL), and Regional Vectorcardiograms (RVCGs) are constructed using the same data recorded by a standard 12‑lead ECG, but they provide additional information not visible in the standard 12‑lead ECG (ECG) tracings.

OBJECTIVES

In previous studies during balloon occlusion of the LAD and RCA, we observed a complete ischemic inversion of the QRS waves, with folding of the loop and ST segment shift. In the present study, we aim to investigate this abnormality using new ECG methods. We hypothesize that utilizing PBL, WUL, and RVCG in patients with ischemia caused by total acute coronary artery occlusion enables the detection of specific abnormalities-such as changes in waveform time/amplitude, the presence of the omega sign, distortion and folding of RVCG loops, and alterations in loop direction in both the transverse and frontal planes-that are not easily discernible with a standard 12‑lead ECG. This enhanced detection aids in understanding the mechanisms underlying electrocardiographic changes and may assist in managing patients when diagnostic uncertainties arise.

METHODS

Thirty-three patients undergoing elective PTCA were studied before and after acute LAD (16 patients) or RCA (17 patients) occlusion, and their data were processed with new methods based on PBLs, WULs, and RVCGs.

RESULTS

1. In acute ischemia due to occlusion of the LAD and RCA, the most important current of injury occurs in the right to left axis. This axis is underestimated by the standard 12‑lead ECG and only partially complemented by leads V3R and V4R. 2. The two-dimensional presentation detects a new sign (the omega sign), not detectable in the classic ECG, but almost always present in ischemia. It also allows for an accurate identification of the J point. 3. Ischemic R wave peak delay results in distortion and folding of the RVCG loop and causes displacement of the J point and the ST segment. 4. Wave inversion changes the loop direction in the transverse and frontal plane.

CONCLUSIONS

Precordial bipolar leads, weighted unipolar leads, and regional vectorcardiograms provide essential information omitted by the standard 12‑lead ECG.

Right ventricle injury in RCA occlusion: Exploration using precordial bipolar leads and surrogate vectorcardiograms

BACKGROUND

Precordial Bipolar Leads (PBL) provide new electrocardiographic information derived from standard 12‑lead ECG recordings.

OBJECTIVES

To explore the usefulness of PBL in patients with acute right coronary artery (RCA) occlusion.

METHODS

Sixteen patients undergoing elective percutaneous transluminal coronary angioplasty (PTCA) were studied before and after RCA occlusion and their data were processed with new methods based on PBL.

RESULTS

The findings were: 1. In PBL V2-V1, strong systolic currents of injury moving in the left to right direction coexist with those directed towards leads II, III and aVF. 2. Changes in the time of the peaks of the QRS waves do not alter the duration of the QRS. 3. The QRS loops of the surrogate VCG generated show that, during ischemia, the time changes in the peak of the QRS waves displayed in one axis are the consequence of an increase in the amplitude of the waves observed in the perpendicular axis. 4. The use of two simultaneous dimensions (transverse and frontal planes) facilitates the location of the J-point. 5. In the surrogate VCGs of this group of patients, J-point and ST segment shifts produced an image that reminded the Greek letter omega (Ω). 6. The QRS wave changes, in time and amplitude, explained the rotational changes and the ischemic distortions of the surrogate VCG loops.

CONCLUSIONS

Computerized processing of ECG data appears to provide new and valuable diagnostic data in patients with acute RCA occlusion. The loops revealed important information related to systolic currents of injury. Because these methods use routine 12‑lead ECG data, the procedure is based only in software applications.

Early ischemic ST-segment and T-wave changes during balloon angioplasty

BACKGROUND

Acute coronary occlusion results in increased T-wave amplitude and ST-segment elevation in the ECG leads facing the ischemic region.

MATERIAL AND METHODS

We performed continuous ECG recording in 34 patients during balloon occlusion of the left anterior descending (LAD), left circumflex (LCx) and right coronary artery (RCA). Delta (Δ) ST and ΔT amplitudes were calculated by subtracting the preinflation values from the values measured during balloon inflation.

RESULTS

Occlusion of the LAD resulted in greater increase in the amplitude of the T wave than of the ST segment in lead V2 (ΔT +3.4 mm, inter-quartile range [IQR] 1-6 mm; ΔST +1.4 mm, 0.5-3 mm). During RCA occlusion, ΔST and ΔT didn't differ significantly. LCx occlusion resulted in significant differences between ΔST and ΔT in all leads, except aVF and V3-V4. In two patients (LCx), we observed a biphasic ST-T response: an initial negative change of the T-wave amplitude was followed by a positive change in leads V1-V2. In leads II, III, aVF and V4-V6, there was an initial positive change, followed by a final negative change towards the end of the occlusion.

CONCLUSION

Continuous 12‑lead ECG recording during balloon occlusion of the LCx resulted in significant differences between the ΔST and ΔT values in all leads except aVF and V3-V4. LAD and RCA occlusion resulted in less evident differences between the ST-segment and T-wave changes. A change in polarity of T-wave changes during balloon occlusion (initial negative and final positive change, or vice versa) proved to be a rare finding.

Abnormal myocardial activation as a cause of ST elevation: A study using Precordial Bipolar Leads (PBL)

OBJECTIVES

The purpose of the study was to describe the ischemic changes occurring during percutaneous transluminal coronary angioplasty (PTCA) using a new method based on Precordial Bipolar Leads (PBL) and Precordial Unipolar Leads (PUL).

BACKGROUND

Ischemic ECG changes have been attributed to both systolic and diastolic injury currents. The relation between ST segment shift and QRS changes is unclear and there is discussion about its significance.

METHODS

Twelve-lead electrocardiograms (ECGs) were performed in 16 patients before PTCA balloon inflation and immediately after balloon deflation in the proximal left anterior descending coronary artery (LAD). Also, ECG data was used to generate V2-V1 PBL, average V1+V2 lead and the correspondent loop in order to explore ECG and spatial vector changes.

RESULTS

1) The V2-V1 vs. Average V1+V2 loop rotation changed from counter clockwise (CCW) to clockwise (CW) in 14/15 patients (93%). 2) In 12/16 patients (75%), there was an abrupt change of QRS vector direction, producing a "folding" of the loop. In 10 of these cases, the change occurred between 32 and 49 milliseconds after the QRS initiation. 3) In 3/16 patients the final part of the loop was "transported", without folding, to the turning point. 4) The "folding" of the loop changed the direction of the final QRS forces and the J point and ST segment were displaced to the left and forward. 5) For this reason, repolarization began from an abnormal anterior location.

CONCLUSIONS

1) Ischemic changes in QRS loop have a cornerstone point in which the whole loop changes. 2) Once the loop has changed its direction, there are no major modifications in the loop development but the forces do not aim anymore to the isoelectric point. 3) Alterations of myocardial activation appear to be responsible of ST elevation in hyperacute ischemia.

Assessing heart disease using a novel magnetocardiography device

The aim of this paper is to present the use of a portable, unshielded magnetocardiograph (MCG) and identify key characteristics of MCG scans that could be used in future studies to identify parameters that are sensitive to cardiac pathology. We recruited 50 patients with confirmed myocardial infarction (MI) within the past 12 weeks and 46 volunteers with no history of cardiac disease. A set of 38 parameters were extracted from MCG features including both signals from the sensor array and from magnetic images obtained from the device and principal component analysis was used to concentrate the information contained in these parameters into uncorrelated predictors. Linear fits of these parameters were then used to examine the ability of MCG to distinguish between sub-groups of patients. In the fist instance, the primary aim of this study was to ensure that MCG has a basic ability to separate a highly polarised patient group (young controls from post infarction patients) and to identify parameters that could be used in future studies to build a formal diagnostic tool kit. Parameters that parameterised left ventricular ejection fraction (LVEF) were identified and an example is presented to show differential low and high ejection fractions.

Prevalence of ECGs Exceeding Thresholds for ST-Segment-Elevation Myocardial Infarction in Apparently Healthy Individuals: The Role of Ethnicity

Background

Early prehospital recognition of critical conditions such as ST‐segment–elevation myocardial infarction (STEMI) has prognostic relevance. Current international electrocardiographic STEMI thresholds are predominantly based on individuals of Western European descent. However, because of ethnic electrocardiographic variability both in health and disease, there is a need to reevaluate diagnostic ST‐segment elevation thresholds for different populations. We hypothesized that fulfillment of ST‐segment elevation thresholds of STEMI criteria (STE‐ECGs) in apparently healthy individuals is ethnicity dependent.

Methods and Results

HELIUS (Healthy Life in an Urban Setting) is a multiethnic cohort study including 10 783 apparently healthy subjects of 6 different ethnicities (African Surinamese, Dutch, Ghanaian, Moroccan, South Asian Surinamese, and Turkish). Prevalence of STE‐ECGs across ethnicities, sexes, and age groups was assessed with respect to the 2 international STEMI thresholds: sex and age specific versus sex specific. Mean prevalence of STE‐ECGs was 2.8% to 3.4% (age/sex‐specific and sex‐specific thresholds, respectively), although with large ethnicity‐dependent variability. Prevalences in Western European Dutch were 2.3% to 3.0%, but excessively higher in young (<40 years) Ghanaian males (21.7%–27.5%) and lowest in older (≥40 years) Turkish females (0.0%). Ethnicity (sub‐Saharan African origin) and other variables (eg, younger age, male sex, high QRS voltages, or anterolateral early repolarization pattern) were positively associated with STE‐ECG occurrence, resulting in subgroups with >45% STE‐ECGs.

Conclusions

The accuracy of diagnostic tests partly relies on background prevalence in healthy individuals. In apparently healthy subjects, there is a highly variable ethnicity‐dependent prevalence of ECGs with ST‐segment elevations exceeding STEMI thresholds. This has potential consequences for STEMI evaluations in individuals who are not of Western European descent, putatively resulting in adverse outcomes with both over‐ and underdiagnosis of STEMI.

An initial exploration of subtraction electrocardiography to detect myocardial ischemia in the prehospital setting

BACKGROUND

In the prehospital triage of patients presenting with symptoms suggestive of acute myocardial ischemia, reliable myocardial ischemia detection in the electrocardiogram (ECG) is pivotal. Due to large interindividual variability and overlap between ischemic and nonischemic ECG-patterns, incorporation of a previous elective (reference) ECG may improve accuracy. The aim of the current study was to explore the potential value of serial ECG analysis using subtraction electrocardiography.

METHODS

SUBTRACT is a multicenter retrospective observational study, including patients who were prehospitally evaluated for acute myocardial ischemia. For each patient, an elective previously recorded reference ECG was subtracted from the ambulance ECG. Patients were classified as myocardial ischemia cases or controls, based on the in-hospital diagnosis. The diagnostic performance of subtraction electrocardiography was tested using logistic regression of 28 variables describing the differences between the reference and ambulance ECGs. The Uni-G ECG Analysis Program was used for state-of-the-art single-ECG interpretation of the ambulance ECG.

RESULTS

In 1,229 patients, the mean area-under-the-curve of subtraction electrocardiography was 0.80 (95%CI: 0.77-0.82). The performance of our new method was comparable to single-ECG analysis using the Uni-G algorithm: sensitivities were 66% versus 67% (p-value > .05), respectively; specificities were 80% versus 81% (p-value > .05), respectively.

CONCLUSIONS

In our initial exploration, the diagnostic performance of subtraction electrocardiography for the detection of acute myocardial ischemia proved equal to that of state-of-the-art automated single-ECG analysis by the Uni-G algorithm. Possibly, refinement of both algorithms, or even integration of the two, could surpass current electrocardiographic myocardial ischemia detection.

Ischemic QRS prolongation as a predictor of ventricular fibrillation in a canine model

OBJECTIVES

An acute coronary occlusion and its possible subsequent complications is one of the most common causes of death. One such complication is ventricular fibrillation (VF) due to myocardial ischemia. The severity of ischemia is related to the amount of coronary arterial collateral flow. In dog studies collateral flow has also been shown to be associated with QRS prolongation. The aim of this study was to investigate whether ischemic QRS prolongation (IQP) is associated with impending VF in an experimental acute ischemia dog model.

METHODS

Degree of IQP and occurrence of VF were measured in dogs (n = 21) during coronary occlusion for 15 min and also during subsequent reperfusion (experiments conducted in 1984).

RESULTS

There was a significant difference in absolute IQP between dogs which developed VF during reperfusion (47 ± 29 ms, mean ± SD) and those which did not (12 ± 10 ms; p = .001).

CONCLUSIONS

IQP during acute coronary occlusion is associated with reperfusion VF in an experimental dog model and might therefore be a potential predictor of malignant arrhythmias in patients with acute coronary syndrome.

Ischemic QRS prolongation as a biomarker of myocardial injury in STEMI patients

BACKGROUND

Patients with acute coronary occlusion (ACO) may not only have ischemia-related ST-segment changes but also changes in the QRS complex. It has recently been shown in dogs that a greater ischemic QRS prolongation (IQP) during ACO is related to lower collateral flow. This suggests that greater IQP could indicate more severe ischemia and thereby more rapid infarct development. Therefore, the purpose was to evaluate the relationship between IQP and measures of myocardial injury in patients presenting with acute ST-elevation myocardial infarction (STEMI).

METHODS

Seventy-seven patients with first-time STEMI were retrospectively included from the recently published SOCCER trial. All patients underwent a cardiac magnetic resonance (CMR) examination 2-6 days after the acute event. Infarct size (IS), myocardium at risk (MaR), and myocardial salvage index (MSI) were assessed and related to IQP. IQP measures assessed were; computer-generated QRS duration, QRS duration at maximum ST deviation, absolute IQP and relative IQP, all derived from a pre-PCI, 12-lead ECG.

RESULTS

Median absolute IQP was 10 ms (range 0-115 ms). There were no statistically significant correlations between measures of IQP and any of the CMR measures of myocardial injury (absolute IQP vs IS, r = 0.03, p = 0.80; MaR, r = -0.01, p = 0.89; MSI, r = -0.05, p = 0.68).

CONCLUSIONS

Unlike previous experimental studies, the IQP was limited in patients presenting at the emergency room with first-time STEMI and no correlation was found between IQP and CMR variables of myocardial injury in these patients. Therefore, IQP does not seem to be a suitable biomarker for triaging patients in this clinical context.

Acute myocardial ischemia monitoring before and during angioplasty by a novel vectorcardiographic parameter set

BACKGROUND

This work evaluates the vectorcardiographic dynamic changes in ischemic patients before and during Percutaneous Transluminal Coronary Angioplasty (PTCA).

METHODS

Four QRS-loop parameters were computed in 51 ischemic and 52 healthy subjects with the objective of assessing the vectorcardiographic differences between both groups: maximum vector magnitude (QRS(mVM)), planar area (QRS(PA)), maximum distance between centroid and loop (QRS(mDCL)) and perimeter (QRS(P)).The conventional ST-change vector magnitude (STC(VM)), QRS-vector difference (QRS(VD)) and spatial ventricular gradient (SVG) were also calculated.

RESULTS

Statistical minute-by-minute PTCA comparison against a healthy population showed that ischemic patients monitoring is greatly enhanced when all the QRS-loop parameters, in combination with the standard STC(VM), QRS(VD) and SVG indexes, are used in the classification. Sensitivity and Specificity, in turn, reached rather high values, 95.4% and 95.2%, respectively.

CONCLUSIONS

These new vectorcardiographic set of complementary QRS-loop parameters, when combined with the classics STC(VM), QRS(VD) and SVG indexes, increase sensitivity and specificity for acute ischemia monitoring.

QRS prolongation on the signal-averaged electrocardiogram versus ST-segment changes on the 12-lead electrocardiogram: which is the most sensitive electrocardiographic marker of myocardial ischemia?

BACKGROUND

ST-segment changes and QRS prolongation are electrocardiographic (ECG) markers of myocardial ischemia.

HYPOTHESIS

This study was undertaken to investigate the appearance of QRS duration changes with or without concomitant ST-segment changes during a typical anginal episode.

METHODS

For this purpose, 126 patients underwent 12-lead surface ECG and signal-averaged electrocardiogram (SAECG) during typical anginal pain as well as at the time the patient was asymptomatic. In both periods, QRS duration and ST-segment changes were evaluated. All patients underwent cardiac catheterization.

RESULTS

Of the 126 patients, 108 (86%) had coronary artery disease (CAD), whereas the remaining 18 (14%) patients had normal coronary arteriograms. During typical anginal pain, 75 of the 108 (70%) patients with CAD and 2 of the 18 (11%) patients with normal coronary arteriograms developed QRS prolongation, whereas 60 of the 108 (56%) patients with CAD and 2 of the 18 (11%) patients with normal coronary vessels developed ST-segment changes. Thus, the sensitivities of QRS prolongation measured by SAECG and of ST-segment changes on the surface ECG for the detection of myocardial ischemia were found to be 70 and 56%, respectively, (p < 0.01), whereas the specificities were both found to be 89% (p = NS).

CONCLUSIONS

During typical anginal pain, QRS prolongation on the SAECG is more sensitive than are ST-segment changes on the ECG for the detection of myocardial ischemia.

Age and gender difference in ST height at rest and after double autonomic blockade in normal adults

BACKGROUND

ST elevation is commonly seen in young, healthy men. The exact mechanisms that cause ST height to be greater in young men are not yet completely understood. The purpose of the present study was to determine whether autonomic tone is responsible for age and gender differences in ST height.

METHODS

Gender and age differences in ST height were studied at rest and after double autonomic blockade (DAB) with atropine and propranolol. Fifty healthy men and women were included (16 men, 14 women, age 23-32 years; 9 men, 11 women, age 65-79 years). Twelve-lead ECGs were registered at rest and after DAB. Leads II and V(1)-V(4) were chosen for analysis. ST height (in mm) was measured manually at the J-point, and 40 ms and 80 ms after the J-point. Values were corrected for QRS amplitude.

RESULTS

Gender and age differences in ST height were seen in both rest and DAB data. Men had greater ST height compared to women at J-point, 40 and 80 ms after the J-point (P < or = 0.0001), and younger subjects had greater ST height than older subjects at J-point (P = 0.0140), 40 and 80 ms after the J-point (P < or = 0.0001). DAB did not change ST height at J-point or at 40 ms, but increased ST height at 80 ms. Women had less of an increase in ST height following DAB than men did.

CONCLUSIONS

ST elevation in the absence of structural or electrical heart disease is mainly seen in young men. Age and gender difference persist after DAB and thus are not due to differences in autonomic tone.

Observer variability and optimal criteria of transient ischemia during ST monitoring with continuous 12-lead ECG

BACKGROUND

ST monitoring with continuous 12-lead ECG is a well-established method in patients with unstable coronary artery disease (CAD). However, the method lacks documentation on optimal criteria for episodes of transient ischemia and on observer variability.

METHODS

Observer variability was evaluated in 24-hour recordings from 100 patients with unstable CAD with monitoring in the coronary care unit. Influence on ST changes by variations in body position were evaluated by monitoring 50 patients in different body positions. Different criteria of transient ischemia and their predictive importance were evaluated in 630 patients with unstable CAD who underwent 12 hours of monitoring and thereafter were followed for 1 to13 months. Two sets of criteria were tested: (1) ST deviation > or = 0.1 mV for at least 1 minute, and (2) ST depression > or = 0.05 mV or elevation > or = 0.1 mV for at least 1 minute.

RESULTS

When the first set of criteria were used, the interobserver agreement was good (kappa = 0.72) and 8 (16%) had significant ST changes in at least one body position. Out of 100 patients with symptoms suggestive of unstable CAD and such ischemia, 24 (24%) had a cardiac event during follow-up. When the second set of criteria were used, the interobserver agreement was poor (kappa = 0.32) and 21 (42%) had significant ST changes in at least one body position. Patients fulfilling the second but not the first set of criteria did not have a higher risk of cardiac event than those without transient ischemia (5.3 vs 4.3%).

CONCLUSIONS

During 12-lead ECG monitoring, transient ischemic episodes should be defined as ST deviations > or = 0.1 mV for at least 1 minute, based on a low observer variability, minor problems with postural ST changes and an important predictive value.

Giant R wave, convex ST-segment elevation, and negative T wave during exercise treadmill test

The giant R wave syndrome is characterized by giant R wave accompanied by widening of the QRS complex, marked ST segment elevation, QRS axis deviation, and the formation of monophasic QRS-ST complex with obliteration of S wave in leads facing the ischemic zone. This report describes a 65-year-old-man with variant angina who had a transient giant R wave syndrome during an exercise treadmill test. Initially, at peak exercise, there was a convex ST segment elevation ending in a negative T wave in the same (inferior) leads which showed giant R waves. Later, in the recovery period and coinciding with an amelioration of myocardial ischemia, there was a less marked increase of R wave amplitude associated with concave ST segment elevation and positive T wave in the inferolateral leads. Subsequently, a ST segment depression in the inferolateral leads preceded the ECG normalization. The patient had also a concave ST segment elevation and positive T wave in inferolateral leads during a spontaneous episode of variant angina at rest. An emergency coronary arteriography showed a dominant right coronary artery with an 80% and a 75% diameter stenosis of the middle and distal segment, respectively; the other arteries and left ventriculogram were normal. The underlying mechanisms of the different shapes of ST segment elevation and T waveform in the setting of acute transmural myocardial ischemia are discussed.

Usefulness of QRS duration in the absence of bundle branch block as an early predictor of survival in non-ST elevation acute myocardial infarction

To determine whether an increased QRS duration in the absence of bundle branch block (BBB) on the presenting electrocardiogram of patients with acute myocardial infarction (AMI) is associated with decreased survival, we retrospectively reviewed 781 consecutive patients admitted to the coronary care unit of our institution with AMI without BBB between 1988 and 1998. In patients with ST elevation AMI (n = 412), the groups with QRS duration > or =100 ms and <100 ms had similar survival. Conversely, in patients with non-ST elevation AMI (n = 369), in-hospital, 1-, 3-, and 5-year survival was 84.4%, 75.6%, 66.7%, and 52.2%, respectively, in the group with QRS > or =100 ms compared with 95.4%, 89.2%, 83.8%, and 74.3%, respectively, in the group with QRS <100 ms (p <0.01, log-rank test). In patients with non-ST elevation AMI, those with QRS duration > or =100 ms were more likely to be men, to have had a prior AMI that healed, to be in Killip class II, III, or IV, and to have lower ejection fraction than patients with QRS duration <100 ms. After adjusting for age, sex, prior AMI or stroke, heart rate, and Killip class on admission, QRS duration > or =100 ms was independently associated with in-hospital and overall mortality in patients with non-ST elevation AMI. QRS duration > or =100 ms in the absence of BBB is an independent predictor of increased mortality in patients with non-ST elevation AMI.

QRS prolongation: a sensitive marker of ischemia during percutaneous transluminal coronary angioplasty

The purpose of this study is to measure QRS duration changes in the human model of ischemia during percutaneous transluminal coronary angioplasty (PTCA) and compare these results to the commonly used ischemia markers, chest pain, and classical ST-T changes. Using a computerized method, QRS duration was measured in 51 patients undergoing elective PTCA. Three milliseconds (msec) or more prolongation of the QRS at peak inflation was considered to be an ischemic response. The results were compared to chest pain and ST-T changes and were analyzed for inflation site within individual coronary arteries. Forty-two patients had a pathological prolongation of the QRS during PTCA. Thirty-two patients developed chest pain, while 19 had ischemic ST-T changes. QRS duration was more prolonged in PTCA to proximal or middle segments of major arteries or their large branches, while it was less prolonged in distal segments or smaller branches. Using our method, QRS prolongation was an ischemia marker in most patients during PTCA and was more sensitive than chest pain or ST-T changes. QRS duration was more prolonged with occlusion of proximal and middle segments of major arteries. Cathet. Cardiovasc. Intervent. 50:177-183, 2000.