Normal and Noninfarct Q Waves

Diagnostic values of inferior Q-waves for myocardial scar identification detected by 3.0 T cardiac MRI

While Q-waves in inferior leads, particularly lead III, can be regarded as a minor abnormality, it can also indicate the presence of myocardial scar. This study assessed the diagnostic value of pathologic inferior Q-waves (lead II, III, aVF) for detecting ischemic scars using a high-resolution 3.0 T cardiac magnetic resonance (CMR). We retrospectively analyzed 1692 patients with suspected or known coronary artery disease who underwent stress CMR perfusion or viability assessment. Pathologic Q-waves were defined as duration of ≥ 30 ms and depth of ≥ 1 mm or QS-complex. Eleven models were created to evaluate the presence of Q-waves in different combinations of inferior leads. Of the 1692 patients, 436 (25.8%) had pathologic Q-waves. Models with Q-waves in leads II + aVF (model 7) and II + III + aVF (model 9) showed high specificity (100% and 99.6%), positive predictive value (PPV) (80.0% and 86.7%), and negative predictive value (NPV) (82.6% and 84.3%) but low sensitivity (1.3% and 13.1%). Other models also maintained high specificity and NPV but poor sensitivity and PPV. Notably, 21% of patients with an isolated pathologic Q-wave in lead III (model 4) exhibited scars. These findings highlight the need for careful clinical assessment when pathologic Q-waves are present.

A Curious Case of Intermittent Negative Deflections Preceding the QRS Complexes

This case report describes a patient in their 60s who developed apparent abnormal Q waves and severe hypomagnesemia while receiving chemotherapy for metastatic rectal carcinoma.

Guide to the Female Student Athlete ECG: A Comprehensive Study of 3466 Young, Racially Diverse Athletes

OBJECTIVES

The 12-lead electrocardiogram (ECG) is used in the preparticipation screening examination for athletes. Despite known differences in ECG findings by sex, only QTc prolongation is given a sex-specific threshold. We hypothesize that our large dataset-with diversity in age, race, and sport participation-can be utilized to improve ECG screening in female student athletes.

METHODS

Computerized 12-lead ECGs were recorded and analyzed in female athletes who underwent preparticipation screening examination between June 2010 and September 2021. The quantitative, empirical 2017 international criteria for electrocardiographic interpretation were compared with either the 99th percentile in our cohort or the percentile that corresponded to the known disease prevalence.

RESULTS

Of 3466 female athletes with ECGs as part of preparticipation screening examination, the 2017 international criteria classified 2.1% of athletes with at least one ECG abnormality requiring cardiological evaluation. Rates were similar across age, race/ethnicity, and sporting discipline. Using ranges based on our population, 2.7% of athletes would require additional workup. Surprisingly, ST depression up to 0.03 mV was a normal finding in this cohort. If RS voltage extremes were considered findings requiring follow-up, an additional 9.6% of the athlete population would be flagged using current definitions. This number decreases to 2.7% if using the 99th percentile in this cohort.

CONCLUSION

These results highlight a difference in the reported prevalence of ECG abnormalities when comparing empirically derived thresholds to statistically derived ranges. Consideration of new metrics specific to the female athlete population has the potential to further refine athlete ECG screening.

A Pseudo-Infarction Pattern in the Setting of Esophageal Malignancy

A 57-year-old African American male was admitted for workup of unintentional weight loss. He was found to have an esophageal squamous cell carcinoma. Electrocardiogram (ECG) readings demonstrated deep Q waves in leads V1-V2 with T wave flattening, which raised concern for a septal infarct. Myocardial infarction (MI) was subsequently ruled out through clinical, imaging, and laboratory analysis. The ECG findings were deemed as a pseudo-infarct pattern in the setting of squamous cell carcinoma of the esophagus.

Infarction or Pseudo-infarction?

An applicant with a history of paroxysmal atrial fibrillation is found to have QS waves in leads III and AVF suggestive of a prior inferior wall myocardial infarction. Using the relationship between Q wave and T wave vectors in the inferior leads, an alternative explanation is explored.

Minor isolated Q waves and cardiovascular events in the MESA study

BACKGROUND

The significance of minor isolated Q waves in the resting electrocardiograms (ECGs) of apparently healthy individuals is unknown.

OBJECTIVE

To examine the association between minor isolated Q waves and incident cardiovascular disease events in the Multi-Ethnic Study of Atherosclerosis (MESA).

DESIGN

This analysis included 6551 MESA participants (38% white, 28% black, 22% Hispanic, 12% Chinese) who were free of cardiovascular disease at enrollment. Cox proportional hazards models were used to examine the association between minor isolated Q waves defined by the Minnesota ECG Classification with adjudicated incident cardiovascular events.

RESULTS

During up to 7.8 years of follow-up, 423 events occurred, with a rate of 10.7 events per 1000 person-years. A significant interaction between minor isolated Q waves and race/ethnicity was observed (P=.030). In models stratified by race/ethnicity and adjusted for demographics, socioeconomic status, common cardiovascular risk factors, and other ECG abnormalities, presence of isolated minor Q waves was significantly associated with incident cardiovascular events in Hispanics (hazard ratio [HR] 2.62; 95% confidence interval [CI], 1.42-4.82), but not in whites (HR 0.65; 95% CI, 0.32-1.33) or blacks (HR 1.46; 95% CI, 0.74-2.89). Despite the statistically significant association in the Chinese population, the small number of events precluded solid conclusions in this race/ethnicity.

CONCLUSION

The prognostic significance of minor isolated Q waves varies across races/ethnicities; they carry a high risk for future cardiovascular events in apparently healthy Hispanics, but not in whites or blacks.

New pathological insights into cardiac amyloidosis: implications for non-invasive diagnosis

BACKGROUND

Knowledge of the patterns of myocardial amyloid accumulation could improve the interpretation of electrocardiographic, echocardiographic and magnetic resonance imaging findings of amyloidosis. We assessed the extent and pattern of myocardial amyloid infiltration in explanted or autopsied hearts of patients with cardiomyopathy related to acquired monoclonal immunoglobulin light-chain (AL) or hereditary transthyretin (TTR) related amyloidosis (ATTR).

METHODS

We analyzed nine explanted/autopsied hearts from patients with AL (n = 4) and ATTR (n = 5) cardiac amyloidosis. For each heart, a biventricular histological macrosection was obtained at mid-ventricular level and analyzed with both inspective and computer-assisted histologic and histomorphometric analysis aimed in particular at quantifying muscle cells, fibrosis and amyloid infiltration.

RESULTS

The extent of amyloid infiltration of the left ventricle (LV) ranged from 45 to 76% (median [interquartile range (IQR)] = 57% [51-64]) of the overall surface. Although LV trabecular and subendocardial were the most infiltrated layers (45-94%, median [IQR] = 73% [67-84] and from 44 to 71%, median [IQR] = 57% [49-59], respectively), intra- and inter-patient heterogeneity was high. Three main patterns of amyloid infiltration of the LV were identified: diffuse (five cases), mainly subendocardial (two cases), and mainly segmental (two cases). The extent of amyloid infiltration of the right ventricle ranged from 48 to 93% (median [IQR] = 61% [59-83]); contributions of parietal and trabecular layers ranged from 32 to 99% (median [IQR] = 63% [47-88]) and from 49 to 93% (median [IQR] = 74% [64-79]), respectively.

CONCLUSIONS

In amyloidotic cardiomyopathy, amyloid deposition is highly heterogeneous. Different patterns of infiltration are identifiable, including diffuse, mainly segmental and mainly subendocardial. Awareness of this variability can help the interpretation of ECGs, echocardiograms and magnetic resonance imaging.

Defining unrecognized myocardial infarction: a call for standardized electrocardiographic diagnostic criteria

BACKGROUND

Unrecognized myocardial infarctions (UMI) are detected by surveillance electrocardiograms (ECGs). In epidemiologic studies, different sets of ECG criteria have been used to define myocardial infarction, possibly contributing to significant differences in prevalence estimates and risk factor associations. We sought to summarize the rationale behind the various UMI-ECG definitions and to suggest an approach to develop uniform criteria.

METHODS

A comprehensive review of relevant publications from 1966 to 2002 was conducted.

RESULTS

Out of 14 major studies, the occurrence of UMI as a proportion of all infarctions varied from 4% to 44%, with markedly varying ECG criteria. No study directly addressed the rationale behind selection of ECG criteria. Computerized ECG analysis appears superior to visual reading due to better reliability, speed and cost while maintaining a similar predictive validity. Criteria requiring only major Q waves have the highest specificity for ECG-MI and for prediction validity for future coronary heart disease in middle-aged white men. The addition of minor Q waves and ST-T abnormalities improves predictive validity in middle-aged women and elderly men. Minor Q waves can have their diagnostic accuracy improved by several strategies, including use of ST-T wave changes, Washington Code, vector cardiogram, chronic obstructive pulmonary disease-ECG criteria, and serial ECG analysis.

CONCLUSION

Currently the most cost-effective and valid method for detecting UMI in epidemiologic studies appears to be computerized ECG analysis using major Q waves in middle-aged white men. Issues needing further research include morphologic validation of ECG-UMI criteria and the influence of age, sex, and race on ECG-MI criteria.

The infarct Q wave: foretaste and aftertaste; presentiment and recall

Since acute myocardial infarction involves a progressive disturbance of intramyocardial propagation the process might be regarded as a conduction disturbance: incomplete in the evolving phase; complete with Q wave inscription. Premature atrial excitation (PAE) can induce fascicular or bundle branch conduction delay, or complete functional block. Considered here are the concepts of foretaste: in which PAE reveals the infarct Q before it has appeared in regular sinus beats, and aftertaste: in which, following the healing of the myocardial infarction, the Q wave is recalled by PAE after it has disappeared from regular beats. Foretaste was observed in a small number of acutely infarcted dogs. Aftertaste is substantially more problematic since Q wave inscription is known to occur, however uncommonly, in a small minority of noninfarcted aberration morphologies. Only lateral infarct Q waves appear to be recallable by PAE.

Intermittent noninfarction Q waves: a finding suggestive of latent preexcitation

OBJECTIVE

To describe 3 patients who presented with chest pain and intermittent Q waves on the electrocardiogram (ECG) and were subsequently found to have latent preexcitation.

PATIENTS AND METHODS

During a span of 8 years, 3 patients were evaluated because of atypical chest pain and pathologic Q waves in the inferior leads; in all 3 patients, the Q waves were intermittent. No patient had a history of arrhythmia or had Wolff-Parkinson-White pattern on the ECG. Diagnostic and therapeutic interventions for suspected myocardial infarction included cardiac catheterization in 2 patients, intravenous thrombolytic therapy in 1 patient, and heparin in 2 patients. Ischemic heart disease was excluded in all. Patients underwent pharmacological testing and/or electrophysiologic study for suspected preexcitation.

RESULTS

Despite the absence of ECG markers of preexcitation, the presence of a latent accessory atrioventricular connection was confirmed in each patient by pharmacological or electrophysiologic studies.

CONCLUSION

In patients who present with intermittent noninfarction Q waves, the most likely diagnosis is latent preexcitation. Clinicians need to be educated about this clinical diagnosis and encouraged to pursue confirmatory testing. Such patients should be informed about the nature and importance of their electrocardiographic abnormality.

Are electrocardiographic Q-wave criteria reliable for diagnosis of perioperative myocardial infarction after coronary surgery?

OBJECTIVE

A major assumption in cardiovascular medicine is that Q-waves on the electrocardiogram indicate major myocardial tissue damage. The appearance of a new Q-wave has therefore been considered the most reliable criterion for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery. In a study, originally intended to evaluate troponin-T as a marker of PMI, analysis of our data aroused the need to address the reliability of Q-wave criteria for diagnosis of PMI.

METHODS

In 302 consecutive patients undergoing coronary surgery, Q-wave and other electrocardiogram (ECG) criteria were compared with biochemical markers of myocardial injury and the postoperative course. All ECGs were analysed by a cardiologist blinded to the biochemical analyses and the clinical course.

RESULTS

The incidence of positive Q-wave criteria was 8.1%. Combined biochemical (CK-MB > or = 70 microg/l) and Q-wave criteria were found in 1.0%. Patients with new Q-waves did not have CK-MB or troponin-T levels significantly different from those without Q-waves. More than 25% of the Q-waves were associated with plasma troponin-T below the reference level (< 0.2 microg/l) on the fourth postoperative day. Q-wave criteria alone did not influence the postoperative course. In contrast, biochemical markers correlated with clinical outcome.

CONCLUSIONS

The majority of Q-waves appearing after coronary surgery were not associated with major myocardial tissue damage, and according to troponin-T one-fourth of the Q-waves were not associated with myocardial necrosis. Furthermore, the appearance of Q-waves had little influence on short term clinical outcome. Therefore, the use of Q-wave criteria as the gold standard for diagnosis of PMI may have to be questioned.

Unexplained gradual-onset Q wave patterns. A case series from the Framingham Study

Original cohort members of the Framingham Study were studied to determine prognosis associated with unexplained (gradual-onset) Q wave patterns detected on routine electrocardiograms (ECGs). Biennial ECGs were obtained on subjects beginning in 1948. The index ECG was read independently and then serially in relation to all previous tracings for evidence of myocardial infarction. Proportional hazards modeling was used to assess the risk for outcomes in those with unexplained (gradual-onset) Q wave patterns compared with subjects with unrecognized myocardial infarcts (abrupt-onset Q waves) and compared with referent subjects. Unexplained Q wave patterns developed in 53 men and 39 women. Subjects with unexplained Q wave patterns had less than 40% of the risk for myocardial infarction or coronary death as compared with those with unrecognized myocardial infarction after adjusting for risk factors (hazard ratio, 0.38; 95% confidence interval, 0.19, 0.78; P = .008) and a trend toward a lower risk for overall mortality (adjusted hazard ratio, 0.73; 95% confidence interval, 0.46, 1.16; P = .18). Risks for myocardial infarction or coronary death and overall mortality were similar in subjects with unexplained Q wave patterns and referent subjects in the fully adjusted models. Detection of prominent Q waves on an ECG requires comparison with prior tracings to differentiate the unexplained Q wave pattern from the unrecognized infarct, conditions that have significantly different prognostic implications.

Nifedipine reduces the incidence of myocardial infarction and transient ischemia in patients undergoing coronary bypass grafting

A randomized study was performed on 104 patients undergoing elective coronary artery bypass grafting to examine whether the infusion of nifedipine (n = 53) reduces the incidence of perioperative myocardial ischemia and necrosis in the early postoperative period. Continuous hemodynamic and three-channel Holter monitoring was performed for 24 hours and serial assessment of serum enzymes and 12-lead electrocardiography were performed for 36 hours postoperatively. Nifedipine (minimum dose, 10 micrograms/kg/hr for 24 hours) was applied from the onset of extracorporal circulation. The control group (n = 51) received nitroglycerin (minimum dose, 1 micrograms/kg/min for 24 hours). Using the combined analyses of electrocardiography and Holter recordings, myocardial ischemia was defined as being either a transient ischemic event (TIE), transient coronary spasm (TCS), or myocardial infarction (MI). The two groups did not differ with respect to preoperative New York Heart Association classification, age, history of myocardial infarction, extracorporal circulation and aortic cross-clamp time, number of distal anastomoses, or systemic and pulmonary hemodynamics. The incidence of perioperative myocardial ischemia was substantially lower in the nifedipine than in the nitroglycerin group [TIE: three of 53 patients (6%) versus nine of 50 patients (18%), p less than 0.001; MI: two of 53 patients (4%) versus six of 50 patients (12%), p less than 0.001; and TCS: none of 53 patients (0%) versus two of 50 patients (4%), p = NS].(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction in Q wave myocardial infarctions with gemfibrozil in the Helsinki Heart Study

The Helsinki Heart Study demonstrated a 34% (p less than 0.02) reduction in the incidence of cardiac end points (myocardial infarction and cardiac death) with the use of gemfibrozil compared with the use of a placebo in dyslipidemic middle-aged men. The major effect was confined to nonfatal myocardial infarctions. In this study we analyzed the effect of gemfibrozil therapy on the incidences of Q wave and non-Q wave infarctions, since the long-term prognoses of these two types of myocardial infarction may be different. The analyses indicated a 45% reduction (P less than 0.02, log-rank test) in the cumulative incidence of Q wave infarctions in the gemfibrozil group without a statistically significant effect on either the rate of non-Q wave infarctions or of coronary deaths. The reduction in the incidence of Q wave infarctions became evident during the second half of the 5-year study period.

Infusion of nifedipine after coronary artery bypass grafting decreases the incidence of early postoperative myocardial ischemia

We performed a randomized study on patients undergoing elective coronary bypass grafting to examine whether postoperative infusion of nifedipine (n = 25) could reduce the incidence of isolated transient myocardial ischemia, myocardial infarction, or both. The control group (n = 25) received nitroglycerin. Hemodynamic and Holter monitoring and serial assessment of enzymatic and electrocardiographic changes were performed for all patients. Both groups showed comparable preoperative and operative data. The incidence of myocardial infarction was significantly lower in the nifedipine group (n = 1) as compared with the control group (n = 4), whereas the number of patients with isolated transient myocardial ischemia was similar in both groups (nifedipine, 3; control, 4). At the time of peak activity, levels of creatine kinase (350 +/- 129 versus 511 +/- 287 IU/mL), creatine kinase-MB (8.4 +/- 5.4 versus 17.1 +/- 11.0 IU/mL), and glutamate-oxaloacetate-transaminase (30.4 +/- 4.4 versus 41.0 +/- 7.9 IU/mL) were markedly lower in the nifedipine group (p less than 0.05). We conclude that infusion of nifedipine after elective coronary artery bypass grafting effectively decreases the incidence of myocardial infarction and the extent of myocardial necrosis during the early postoperative period.