Can the surface electrocardiogram be used to predict myocardial viability?

Revisiting the diagnostic and prognostic significance of high-frequency QRS analysis in cardiovascular diseases: a comprehensive review

Cardiovascular diseases (CVDs) present a significant global public health threat, contributing to a substantial number of cases involving morbidity and mortality. Therefore, the early and accurate detection of CVDs plays an indispensable role in enhancing patient outcomes. Decades of extensive research on electrocardiography at high frequencies have yielded a wealth of knowledge regarding alterations in the QRS complex during myocardial ischemia, as well as the methodologies to assess and quantify these changes. In recent years, the analysis of high-frequency QRS (HF-QRS) components has emerged as a promising non-invasive approach for diagnosing various cardiovascular conditions. Alterations in HF-QRS amplitude and morphology have demonstrated remarkable sensitivity as diagnostic indicators for myocardial ischemia, often surpassing measures of ST-T segment changes. This comprehensive review aims to provide an intricate overview of the current advancements, challenges, and prospects associated with HF-QRS analysis in the field of CVDs.

Non-invasive Imaging in Patients With Chronic Total Occlusions of the Coronary Arteries-What Does the Interventionalist Need for Success?

Chronic total occlusion (CTO) of coronary arteries is a common finding in patients with known or suspected coronary artery disease (CAD). Although tremendous advances have been made in the interventional treatment of CTOs over the past decade, correct patient selection remains an important parameter for achieving optimal results. Non-invasive imaging can make a valuable contribution. Ischemia and viability, two major factors in this regard, can be displayed using echocardiography, single-photon emission tomography, positron emission tomography, computed tomography, and cardiac magnetic resonance imaging. Each has its own strengths and weaknesses. Although most have been studied in patients with CAD in general, there is an increasing number of studies with positive preselectional factors for patients with CTOs. The aim of this review is to provide a structured overview of the current state of pre-interventional imaging for CTOs.

Value of 12-lead electrocardiogram to predict myocardial scar on FDG PET in heart failure patients

PURPOSE

A surface 12-lead electrocardiogram (ECG) is widely available, fast, inexpensive, and safe. However, its value to predict a true myocardial scar in patients with ischemic cardiomyopathy (ICM) has not been studied extensively yet. This study was conducted to assess whether Q waves on resting surface 12-lead ECG are predictive of non-viable myocardium in patients with ICM.

METHODS

We analyzed resting ECGs of 149 patients with ICM undergoing cardiac positron emission tomography (PET) with 13N-ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) at our institution. Pathological Q waves and QS complexes were assigned to one of three coronary artery territories and compared to the PET findings. Myocardial scar was defined as 2 or more contiguous myocardial segments with an average (matched) reduction of NH3 and FDG uptake <50% of the maximum value.

RESULTS

Pathological Q waves had a sensitivity and specificity of 70% and 40%, respectively, and a PPV and NPV of 37% and 73%, respectively, to detect myocardial scar on FDG PET. For QS complexes, sensitivity and specificity were 46% and 59%, respectively, and PPV and NPV were 36% and 68%, respectively. Sensitivity was lower, but specificity was significantly higher in both the LCX and RCA compared to the LAD territory (p<0.001), particularly for QS complexes.

CONCLUSION

Pathological Q waves on resting 12-lead ECG have poor or at best moderate sensitivity and specificity to detect myocardial scar on FDG PET. These findings support the use of more advanced imaging techniques to assess myocardial viability in ICM.

Value of pathologic Q wave in surface electrocardiography in the prediction of myocardial nonviability: A cardiac magnetic resonance imaging-based study

In surface electrocardiography (ECG), Q wave is often considered as a sign of irreversibly scarred myocardium. Cardiac magnetic resonance (CMR) imaging is an accurate mean for the detection of myocardial viability. Herein, we study the predictive value of Q wave in nonviable (scarred) myocardium by CMR study. Retrospective analysis of the ECG and CMR data of 35 coronary artery disease patients was performed. The delayed enhancement CMR protocol was used for the detection of viability. The presence of a pathologic Q wave in surface ECG was negatively related to myocardial viability with a kappa measurement of agreement of −0.544 and P < 0.0001. Pathologic Q wave in surface ECG can be used as a simple tool for myocardial viability prediction.

Gated metabolic myocardial imaging, a surrogate for dual perfusion-metabolism imaging by positron emission tomography

Objective

Perfusion-metabolism mismatch pattern on positron emission tomography (PET) predicts hibernating myocardium. We assess the ECG-gated metabolic PET as a surrogate for the perfusion-metabolism mismatch pattern on PET imaging.

Methods

¹³N-Ammonia (NH₃) and ¹⁸F-fluorodeoxyglucose (FDG) are respectively perfusion and metabolism PET tracers. We used ECG gating to acquire FDG-PET to collect wall thickening (mechanical) data. These allow detection of metabolic activity in regions with reduced contraction (metabolism-mechanical mismatch pattern). We had two data sets on each patient: perfusion-metabolism and metabolism-mechanical data sets. We tested the hypothesis that metabolism-mechanical pattern on PET could predict perfusion-metabolism mismatch pattern.

Results

We studied 55 patients (48 males), mean age 62 years. All were in sinus rhythm, and had impaired left ventricular contraction. Perfusion-metabolism mismatch pattern was found in 26 patients. Metabolism-mechanical mismatch pattern was found in 25 patients. The results were concordant in 52 patients (95%). As a surrogate for perfusion-metabolism mismatch pattern, demonstration of metabolism-mechanical mismatch pattern is highly sensitive (92%) and specific (97%). In this cohort, the positive and negative predictive accuracy of the new method are 96% and 93%, respectively.

Conclusion

Metabolism-mechanical mismatch pattern could predict perfusion-metabolism mismatch pattern in patients with myocardial viability criteria on PET. Prospective validation against the gold standard of improved myocardial contraction after revascularisation is needed.

Myocardial Viability: From Proof of Concept to Clinical Practice

Ischaemic left ventricular (LV) dysfunction can arise from myocardial stunning, hibernation, or necrosis. Imaging modalities have become front-line methods in the assessment of viable myocardial tissue, with the aim to stratify patients into optimal treatment pathways. Initial studies, although favorable, lacked sufficient power and sample size to provide conclusive outcomes of viability assessment. Recent trials, including the STICH and HEART studies, have failed to confer prognostic benefits of revascularisation therapy over standard medical management in ischaemic cardiomyopathy. In lieu of these recent findings, assessment of myocardial viability therefore should not be the sole factor for therapy choice. Optimization of medical therapy is paramount, and physicians should feel comfortable in deferring coronary revascularisation in patients with coronary artery disease with reduced LV systolic function. Newer trials are currently underway and will hopefully provide a more complete understanding of the pathos and management of ischaemic cardiomyopathy.

Prognostic significance of silent myocardial infarction in newly diagnosed type 2 diabetes mellitus: United Kingdom Prospective Diabetes Study (UKPDS) 79

BACKGROUND

We aimed to determine the prevalence of silent myocardial infarction (SMI) in people with newly diagnosed type 2 diabetes mellitus and its relationships to future myocardial infarction (MI) and all-cause mortality.

METHODS AND RESULTS

We examined data from the 5102 patients in the 30-year UK Prospective Diabetes Study (UKPDS) and used Cox proportional hazards regression to examine outcomes by SMI status. Of 1967 patients with complete baseline data, 326 (16.6%) had ECG evidence of SMI (Minnesota codes 1.1 or 1.2) at enrollment. Those with SMI were more likely to be older, female, sedentary, and nonsmokers compared with those without SMI. Their mean blood pressure was greater despite more intensive antihypertensive treatment; they were more likely to be taking aspirin and lipid-lowering therapy; and they had a greater prevalence of microangiopathy. Fully adjusted hazard ratios for those with versus those without SMI in multivariate models that included UKPDS Risk Engine variables were 1.58 (95% confidence interval, 1.22-2.05) for fatal MI and 1.31 (95% confidence interval, 1.10-1.56) for all-cause mortality. Hazard ratios for first fatal or nonfatal MI and for first nonfatal MI were nonsignificant. The net reclassification index showed no improvement when SMI was added to these models, and the integrated discrimination index showed that SMI marginally improved the prediction of fatal MI and all-cause mortality.

CONCLUSIONS

About 1 in 6 UKPDS patients with newly diagnosed type 2 diabetes mellitus had evidence of SMI, which was independently associated with an increased risk of fatal MI and all-cause mortality. However, identification of SMI does not add substantively to current UKPDS Risk Engine predictive variables.

CLINICAL TRIAL REGISTRATION

URL: http://www.controlled-trials.com. Identifier: ISRCTN number 75451837.

A cardiac magnetic resonance imaging study of electrocardiographic Q waves in type 2 diabetes: the Fremantle Diabetes Study

To investigate the evolution and significance of Q waves in type 2 diabetes, we studied 36 patients of mean (+/-S.D.) age 69.9+/-7.1 years from the longitudinal observational Fremantle Diabetes Study (FDS). All had (i) neither history/symptoms of coronary heart disease (CHD) nor pathological Q waves at FDS recruitment between 1993 and 1996, (ii) five consecutive annual assessments by FDS close-out in 2001, and (iii) contrast-enhanced cardiac magnetic resonance imaging in 2005. At this latter assessment, there were (i) 9 with no history of CHD or Q waves during follow-up (Group 1), (ii) 13 with Q waves on >/=1 electrocardiogram but no CHD history/symptoms (Group 2), and (iii) 14 with CHD history/symptoms irrespective of electrocardiographic status (Group 3). Of 20 episodes of new Q waves in 17 Group 2 or Group 3 patients during FDS follow-up, 17 (85%) resolved within 2 years. A myocardial infarction (MI) was detected by CMR in three patients (8.3%; one subendocardial in Groups 1 and 3, one non-full-thickness in Group 3) but these did not correlate with electrocardiographic appearances. Q waves may have unreliable pathological significance in type 2 diabetes, including as a marker of silent MI.

Lack of sensitivity of the electrocardiogram for detection of old myocardial infarction: a cardiac magnetic resonance imaging study

BACKGROUND

The presence of Q waves in the electrocardiogram (ECG) has been used as a marker of prior myocardial infarction (MI). Its accuracy, however, is uncertain. The purpose of this study is to determine the accuracy of an ECG to detect prior MI compared with a novel criterion standard.

METHODS

This study conducted retrospective inclusion with de novo analysis of ECG and cardiac magnetic resonance (CMR) by independent blinded readers in a single-institution setting. The population consisted of a consecutive sample of 146 patients referred for CMR for evaluation of myocardial viability and necrosis. Q/QS waves on ECG were defined as per Minnesota Code criteria. Myocardial scar was quantified and localized by CMR delayed contrast hyperenhancement and assumed as criterion standard. Sensitivity, specificity, and predictive values of ECG were calculated for different scar sizes (>1%, >15%, and >30% of the myocardium) and location (global, anterior, inferior, and lateral walls).

RESULTS

Sensitivity was 48.4%; specificity, 83.5; positive predictive accuracy, 72.0%; and negative predictive accuracy, 64.2%. Sensitivity improved when only large infarcts were considered (64.2%), but specificity decreased to 72.7%. Sensitivity for detecting isolated anterior or inferior wall scars was similar, but isolated lateral wall scar was rarely identified (14.3%). When all 3 walls were involved, sensitivity was still low at 57.9%.

CONCLUSIONS

The lack of sensitivity and the resulting low negative predictive value of Q/QS criteria seriously limit its accuracy as a marker of prior MI.

Twelve-lead electrocardiogram: The advantages of an orderly frontal lead display including lead −aVR

BACKGROUND

It is possible that efforts in ECG review by both young experienced clinicians are currently discouraged-and risk to be completely dismissed-by the conventional (ie, disorderly) display of the frontal plane leads, with lead aVR at -150 degrees.

METHODS

We reviewed studies on the usefulness of leads aVR and -aVR as well as on the history of the frontal leads in electrocardiography.

RESULTS

Lead aVR and particularly, lead -aVR, provide useful information when systematically analyzed. In addition, if lead -aVR is examined in its anatomically logical sequence, ie, aVL, I, -aVR, II, aVF, and III, the frontal plane of the 12-lead ECG is more easily understood. This "panoramic" or "orderly" display is in common use in countries such as Sweden, but it is rarely seen in the United States.

CONCLUSIONS

ECG interpretation would be enhanced by displaying the limb leads in an orderly arrangement that starts with lead aVL and ends with lead III, and many ECG changes would be ideally displayed by a lead -aVR at 30 degrees.