Innovative Technologies

Hiroaki Shimokawa, M.D., Professor
Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine

The mortality rate from ischemic heart disease in Japan has been reported to be 63.4 and 50.0 per 100,000 in males and females, respectively. According to the MONICA Study, it is estimated that the morbidity rates of myocardial infarction (MI) per year are approximately 38 (20-50) and 12 (10-30) in males and females, respectively (Guidelines for the Management of Patients with ST-elevation Myocardial Infarction; Japanese Circulation Society). Needless to say, diagnosis of ischemic heart disease and acute MI is very important.

Moreover, these guidelines also refer to the importance of the electrocardiograph (ECG) in the management of these diseases, especially in recording V4R to evaluate possible right ventricular MI and leads V7, V8 and V9 to evaluate possible posterior infarction. However, these leads are rarely measured in routine diagnostic procedures. The synthesized 18-lead ECG to be introduced shows the measurements for the right-side precordial leads V3R, V4R and V5R and posterior leads V7, V8 and V9 calculated from measurement of the standard 12-lead ECG. I believe that combining these synthesized extended leads with the standard 12-lead ECG will enable easier detection of right ventricular MI and posterior infarctions than when only using the standard 12-lead ECG.

Daming Wei, Ph.D., Professor
Director of Biomedical Information Technology Lab, The University of Aizu

Synthesized ECG for Extended Posterior and Right Precordial Leads − Principle and Clinical Applications
While 12-lead electrocardiogram (ECG) is a clinical standard, it is not sensitive enough to detect some disorders like acute myocardial infarction (AMI) taking place on the posterior or right ventricular walls. In such circumstances, ECG waveforms recorded from extended leads on V7, V8 and V9, or V3R, V4R, V5R and V6R are usually desired. However, it is not only a very complicated process to attach electrodes on the back of the body, but also a standard 12-lead electrocardiograph is not capable of recording ECG from extended leads during routine clinical recording.

We present a work that synthesizes the ECG waveforms of the extended leads of V7, V8 and V9, or V3R, V4R and V5R using ECG signals from standard 12-lead ECG recording. The theoretical principle of synthesis is based on information redundancy, so that the extended leads can be expressed by a linear combination of the recorded leads for the 12-lead ECG. We evaluated our method using several hundreds of clinical ECG data recorded by Tohoku University Hospital, Nihon University Hospital, and other medical centers. Accuracy that satisfied the standard for clinical application was obtained, which included correlations of waveforms, and potential differences between the synthesized and measured ECGs. The figure shows an example where the detected and synthesized ECG waveforms of extended leads are overlapped. This study provides a computer-aided means for diagnosis of posterior and right ventricular AMI without having to record posterior and right precordial ECGs.

Takao Kato, M.D., Professor
Department of Internal Medicine, Nippon Medical School
Synthesized 18-lead ECG, which I presented as research findings at a symposium of the International Society of Holter and Noninvasive Electrocardiology in 2009, is to be introduced as an ECG viewer on the PC, and I have high expectations for its future applications at actual sites.

This synthesized 18-lead ECG method derives the measurements of right-side leads V3R, V4R and V5R and posterior leads V7, V8 and V9 using ECG signals from standard 12-lead ECG recording. Here I’d like to introduce one of the cases reported by the clinic of Nippon Medical School, where I found this method to be useful in routine diagnosis.
Figure 1 is an ECG of a patient (60 years old, male) with chest pain obtained at the initial visit on March 8, 2008.

As shown in Fig.1, ST elevation appears in leads II, III and aVF of standard 12-lead ECG, which indicates the patient has an inferior infarction while the diagnosis of right ventricular MI is uncertain since the ST change is less pronounced in leads aVR, V1 and V2. In contrast, derived right-side precordial leads (V3R, V4R, and V5R; Synthesized) clearly show ST elevation, which strongly indicates the patient has right ventricular MI.
Actual ECG waveforms (V3R, V4R, and V5R; Actual) recorded by actually placing electrodes also shows ST elevation, which indicate good consistency between the Synthesized and Actual ECG waveform. Therefore, it can be said that these derived right-side precordial leads reflect the status of right ventricular MI well although it would be difficult to diagnose MI that extended to the right ventricule using only standard 12-lead ECG.

When MI is suspected in clinical settings, it is obviously critical to determine the infarcted area at an early stage and provide appropriate treatment promptly.This easy-to-use synthesized 18-lead ECG method is clinically useful for evaluating the status of the right ventricule and posterior wall of the heart, which is difficult for standard 12-lead ECG.

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