Gender Differences Between the Minnesota Code and Novacode Electrocardiographic Prognostication of Coronary Heart Disease in the Cardiovascular Health Study




The Minnesota Code (MC) and Novacode (Nova) are the most widely used electrocardiographic (ECG) classification systems. The comparative strengths of their classifications for Q- and ST-T–wave abnormalities in predicting coronary heart disease (CHD) events and total mortality have not been evaluated separately by gender. We studied standard 12-lead electrocardiograms at rest from 4,988 participants in the Cardiovascular Health Study. Average age at baseline was 73 years, 60% of participants were women 85% were white, and 22% had a history of cardiovascular disease or presence of ECG myocardial infarction by MC or Nova. Starting in 1989 with an average 17-year follow-up, 65% of participants died and 33% had incident CHD in a cohort free of cardiovascular disease at baseline. Of these, electrocardiograms with major Q-wave or major ST-T abnormalities by MC or Nova predicted increased risk for CHD events and total mortality with no significant differences in predictability between men and women. The study also found that women had fewer major Q-wave changes but more major ST-T abnormalities than men. However, there were no gender differences in predicting CHD events and total mortality. In conclusion, ECG classification systems for myocardial infarction/ischemia abnormalities by MC or Nova are valuable and useful for men and women in clinical trials and epidemiologic studies.


Electrocardiographic (ECG) criteria for myocardial infarction and ischemia have been used as evidence for coronary heart disease (CHD) in epidemiologic studies and clinical trials and are a powerful index for assessment of cardiovascular disease (CVD) risk and an important predictor for total mortality. Comparative strengths of their classification by the Minnesota Code (MC) and the Novacode (Nova), have not been evaluated separately by gender. The present study evaluated the value of current MC and Nova for myocardial infarction/ischemia for prediction of incident fatal and nonfatal cardiac events and total mortality and compared the predictive power of each coding system in men and women.


Methods


The Cardiovascular Health Study (CHS) is a population-based prospective cohort study of risk factors for CHD and stroke in men and women ≥65 years of age in 4 United States communities that started in 1989. Eligible participants were sampled from Medicare-eligibility lists in each area. Details of the study design have been described previously. Eligible participants gave informed consent, and study protocols were approved by institutional review boards at participating institutions. Of 5,888 ECG recordings available from baseline examinations of the CHS cohort, those with incomplete data or inadequate quality and QRS duration ≥120 ms were excluded. The remaining 4,988 participants at baseline were classified into 2 groups, a CVD group (n = 1,113) and a CVD-free group (n = 3,875). CVD at baseline was defined by the presence of ECG myocardial infarction evidence by MC or Nova, a history of clinical myocardial infarction, angina pectoris that was confirmed by retrospective review of hospitalization medical records, or self-report of coronary angioplasty or bypass surgery. Average follow-up was 17 years (maximum 18). Three outcomes were considered in the present analysis: incident CHD events (fatal and nonfatal), CHD death, and all-cause mortality. After baseline, deaths and hospitalization events were ascertained by semiannual follow-up telephone calls to cohort members, review of vital records, and community surveillance of hospitalized and fatal events. The CHS mortality review committee reviewed and adjudicated all fatal events.


Identical electrocardiographs (MAC PC, Marquette Electronics, Inc., Milwaukee, Wisconsin) were used in all clinic sites. Standard 12-lead electrocardiograms at rest were recorded in all participants using strictly standardized procedures. All electrocardiograms were processed in a central laboratory (Epidemiologic Cardiology Research Center, Wake Forest University, Winston-Salem, North Carolina) and were classified by the Nova and MC using the 2001 version of the GE Marquette 12-SL program. ECG classification criteria for myocardial infarction/ischemia by Nova/MC in the present study were the same as previously described. Nova myocardial infarction was identified by Nova codes 5.1 to 5.4 and ECG major Q/ST-T changes by Nova was identified as Nova codes 5.1 to 5.6. Similarly, MC myocardial infarction was identified by categories C.1 to C.4 to match Nova myocardial infarction. ECG major Q/ST-T change by MC was identified as categories C.1 to C.6 ( Table 1 ).



Table 1

Electrocardiographic criteria for myocardial infarction and ischemia by Novacode and Minnesota Code




















































Category Novacode Minnesota Code
Major Q waves 5.1 C.1
Moderate Q waves with ST-T abnormalities 5.2 C.2
Moderate Q waves without ST-T abnormalities 5.3 C.3
Minor Q waves with ST-T abnormalities 5.4 C.4
Isolated/major ST abnormalities 5.5 C.5
Isolated/major T wave abnormalities 5.6 C.6
Minor Q waves 5.7 C.7
Minor ST-T abnormalities 5.8 C.8
No significant Q waves or ST-T 5.0 C.0
Electrocardiographic myocardial infarction by Novacode and Minnesota Code 5.1–5.4 C.1–C.4
ECG major Q or major ST-T abnormalities by Novacode and Minnesota Code 5.1–5.6 C.1–C.6

See Zhang et al for detailed definition.

C standard for combined code of Minnesota Codes 1, 4, and 5 to match hierarchical codes in Novacode 5.



CVD and CVD-free groups at baseline were analyzed separately. Cox proportional hazards regression models were used to test and compare the MC and Nova for myocardial infarction/ischemia and ECG abnormality classifications as predictors of each of the 3 study end points after adjustment for demographic and clinical variables. Clinical and demographic characteristics that were significantly associated with risk of CHD event or total mortality were included in the multivariate model to determine if ECG predictors for risk of CHD events and total mortality differed between women and men and between CVD and CVD-free groups at baseline, which are listed in Tables 2 and 3 . All analyses were performed with SAS 9.1.3 (SAS Institute, Cary, North Carolina).



Table 2

Baseline electrocardiographic findings by Novacode and Minnesota Code criteria and outcomes during average 17-year follow-up

































































































































































































































































Characteristics Total(n = 4,988) Prevalent CVD Group CVD-Free Group
Women Men p Value Women Men p Value
(n = 561) (n = 552) (n = 2,416) (n = 1,459)
Age (years) 73 ± 6 74 ± 6 74 ± 6 0.5846 72 ± 5 73 ± 6 0.0001
Body mass index (kg/m 2 ) 27 ± 5 27 ± 5 27 ± 4 0.0414 27 ± 5 26 ± 4 0.0364
Systolic blood pressure (mm Hg) 136 ± 22 141 ± 24 135 ± 21 <0.0001 136 ± 22 135 ± 21 0.5097
Diastolic blood pressure (mm Hg) 71 ± 11 69 ± 12 71 ± 11 0.0416 70 ± 11 73 ± 11 <0.0001
African-American 15.4% 20.7% 10.0% <0.0001 15.7% 14.9% 0.5563
Current smoking 12.2% 13.0% 9.1% <0.0001 12.8% 12.0% <0.0001
Hypertension 57.8% 72.7% 61.4% <0.0001 56.4% 52.9% 0.0356
Diabetes mellitus 15.6% 20.6% 25.5% 0.0542 12.2% 15.5% 0.0030
Total mortality 64.9% 73.8% 83.3% 0.0001 56.5% 68.3% <0.0001
Coronary heart disease death 15.6% 22.1% 29.7% 0.0037 10.6% 16.2% <0.0001
Incident coronary heart disease 32.6% 28.9% 38.6% <0.0001
Myocardial infarction/ischemia by Novacode/Minnesota Code
Myocardial infarction by Novacode/Minnesota Code 8.9% 35.7% 44.0% 0.0043
Major Q wave by Novacode/Minnesota Code 6.7% 24.2% 35.7% <0.0001
Major ST-T change by Novacode/Minnesota Code 15.2% 35.1% 29.4% 0.0396 10.7% 9.7% 0.3484
Major Q/ST-T change by Novacode/Minnesota Code 20.2% 52.6% 56.5% 0.2085 10.7% 9.7% 0.3484
Major Q/ST-T change by Novacode
Myocardial infarction by Novacode 6.3% 23.5% 33.0% 0.0005
Major Q wave by Novacode 4.1% 13.4% 23.0% <0.0001
Major ST-T change by Novacode 14.4% 33.7% 28.8% 0.0789 9.6% 9.5% 0.9160
Major Q/ST-T change by Novacode 17.5% 43.5% 47.1% 0.2271 9.6% 9.5% 0.9160
Major Q/ST-T change by Minnesota Code
Myocardial infarction by Minnesota Code 7.8% 31.2% 39.0% 0.0067
Major Q wave by Minnesota Code 6.4% 23.7% 33.7% 0.0002
Major ST-T change by Minnesota Code 12.2% 28.9% 22.8% 0.0212 8.9% 7.2% 0.0564
Major Q/ST-T change by Minnesota Code 17.8% 49.0% 52.5% 0.2411 8.9% 7.2% 0.0564

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Dec 22, 2016 | Posted by in CARDIOLOGY | Comments Off on Gender Differences Between the Minnesota Code and Novacode Electrocardiographic Prognostication of Coronary Heart Disease in the Cardiovascular Health Study

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