ECG myocardial infarct size: a gender-, age-, race-insensitive 12-segment multiple regression model. I: Retrospective learning set of 100 pathoanatomic infarcts and 229 normal control subjects

Ethnic differences in electrocardiographic amplitude measurements

BACKGROUND

There is controversy regarding ethnic differences in electrocardiographic (ECG) patterns because of potentially confounding socioeconomic, nutritional, environmental and occupational factors.

METHODS

We reviewed the first 1000 medical files of a multi-ethnic community, where all individuals shared similar living conditions. Only healthy adults age 15 to 60 years were included. Wave amplitudes were measured manually from the standard 12 lead ECG. Minnesota coding was used.

RESULTS

ECGs from 597 subjects were included in the study: 350 Saudi Arabians, 95 Indians, 39 Jordanians, 17 Sri-Lankans, 39 Filipinos, and 57 Caucasians; 349 were men. The mean+/-SD of Sokolow-Lyon voltage (SLV) in men was significantly different among ethnic groups (2.9+/-0.86, 2.64+/-0.79, 2.73+/-0.72, 3.23+/-0.61, 2.94+/-0.6, 2.58+/-0.79 mV; P=0.0006, for Saudis, Indians, Jordanians, Filipinos, Sri-Lankans, and Caucasians, respectively). SLV was similar among ethnic groups in women. The prevalence of early transition patterns was also different among ethnic groups in men but not women (15.8%, 34.6%, 17.9%, 21.7%, 35.3%, 26.8% in Saudi, Indian, Jordanian, Filipino, Sri-Lankan, and Caucasian men, respectively, P=0.037). T wave amplitude was significantly different among ethnic groups in selected leads.

CONCLUSIONS

ECG wave amplitude differs with ethnic origin even when other factors are similar. Using SLV of 3.5 mV as a criterion may overestimate the incidence of left ventricular hypertrophy in some ethnic groups. The pattern of high R wave in lead V1 is common in healthy adults in certain ethnic groups. T wave height differs with ethnic origin and sex.

Quantitative clinical assessment of chronic anterior myocardial infarction with delayed enhancement magnetic resonance imaging and QRS scoring

BACKGROUND

Both the regional and global myocardial extent of chronic myocardial infarction (MI) are important prognostic factors for length and quality of life and also crucial for the choice of therapy in patients with ischemic heart disease. Our aim was to develop and validate techniques for comparison between regional and global size of remote anterior MI in the left ventricle quantified with both magnetic resonance imaging (MRI) and electrocardiogram (ECG).

METHODS

Delayed-enhancement (DE) MRI was used as a clinical "gold standard" for MI size to evaluate the extent of MI estimated with the commonly available standard 12-lead ECG. A method for comparing global and regional quantifications of MI with DE-MRI and ECG was developed. The Selvester QRS-scoring system was used for estimating MI size electrocardiographically.

RESULTS

Twenty-five patients with chronic single anterior MI, documented with DE-MRI, were studied. The best agreement for mean % MI per regional segment of the left ventricle was found in the middle third (26% vs 27%), whereas the most significant discrepancy was found in the apex (56% vs 30%). The global MI size of the left ventricle averaged 21 +/- 9% with DE-MRI and 22% +/- 12% with ECG, with a correlation of r = 0.40 (P <.05).

CONCLUSIONS

The current Selvester QRS scoring system performs well for quantifying anterior MI in the mid-regions of the left ventricle. The diagnostic performance of the Selvester QRS-scoring system for quantifying MI in the other regions, particularly the left ventricular apex, can potentially be improved, with DE-MRI as the gold standard.

Comparison of the various electrocardiographic scoring codes for estimating anatomically documented sizes of single and multiple infarcts of the left ventricle

It is clinically important to estimate the size of a myocardial infarction (MI) to predict patient prognosis, to determine the ability of a therapy to limit its size, and to evaluate its effect on left ventricular function. Various electrocardiographic methods have been used for these purposes but their accuracies have not been compared with each other using an identical reference population of anatomically measured infarcts. The capability of 4 electrocardiographic scoring methods (the Selvester score, the Minnesota code, the Novacode, and the Cardiac Infarction Injury Score) to estimate MI size was compared using anatomic MI size in a group of 100 deceased patients. All patients had a standard 12-lead electrocardiogram of sufficient quality to perform manual waveform measurements and without confounding factors such as ventricular hypertrophy, fascicular block, or bundle branch block. The location and size of the left ventricular infarction was measured postmortem using the anatomic method of Ideker et al. All methods' size estimates correlated best with anatomic MI size in the anterior location (r = 0.65 to 0.89). The Selvester score was superior in estimating the sizes of inferior (r = 0.70) and posterolateral (r = 0.74) infarcts. For multiple infarcts all methods performed poorly (r = 0.18 to 0.44).

The standard 11-lead ECG. Neglect of lead aVR in the classical limb lead display

This study investigates how the format of limb lead display influences electrocardiographic (ECG) interpretation. The positive aspect of lead aVR (included in the classical display) is directed opposite to that of the other leads. This could lead to an ECG interpreter's disregard of lead aVR, thus providing a "standard 11-lead ECG." It is hypothesized that when using the classical limb lead display, ECG interpreters often ignore lead aVR, even when considering complex ECGs. Thirty-five of the participants attending this International Society of Computerized Electrocardiology meeting were asked to interpret five complex ECGs, displayed in the classical format. Lead aVR had been replaced by lead -aVR on all of these recordings. Second, the participants were asked if they (1) used all 12 leads, (2) used lead aVR, and (3) noticed that lead aVR had been changed. The results indicate that a vast majority of interpreters (80-94%) did not detect when lead aVR had been reversed. This suggests that interpreters only use 11 of the standard leads when presented with the classical display method to evaluate clinical problems.