Prognostic Value of Ischemia Monitoring with On-Line Vectorcardiography in Patients with Unstable Coronary Artery Disease

Abstract

Aim: The aim of this study was to determine whether on-line vectorcardiography (VCG) gives independent prognostic information, regarding death, myocardial infarction (MI), and revascularization in patients with unstable coronary artery disease, i.e. unstable angina or non-Q-wave MI. Methods and Results: One hundred and fifty patients (mean age 69 ± 10), participating in a randomized study of low-molecular-weight heparin in unstable coronary artery disease, were studied with on-line VCG recordings for 24 h. During a 5–6-month follow-up, 11 patients died, 14 suffered a nonfatal MI and 31 were revascularized. Univariate predictors of death were diabetes mellitus (p < 0.01), maximum ST vector magnitude (ST-VM; p < 0.001), maximum ST change vector magnitude (STC-VM; p < 0.001), number of ST-VM (p < 0.01) and STC-VM episodes (p < 0.001). In multivariate analysis, the number of STC-VM episodes (p < 0.01) and diabetes mellitus (p < 0.02) each gave independent prognostic information regarding death. When all cardiovascular events were combined, the inhability to perform an exercise test (p < 0.05), maximum value of ST-VM (p < 0.01) and STC-VM (p < 0.001), the number of episodes of STC-VM (p < 0.001) and ST-VM (p < 0.001) all gave prognostic information. In multivariate analysis, the inability to perform an exercise test and the number of STC-VM episodes were independent predictors. Conclusion: VCG monitoring during the first 24 h of hospitalization for unstable coronary artery disease gives independent prognostic information.

A Technical Approach for Optimizing Surveillance of Patients with Unstable Coronary Syndromes: Continuous Vectorcardiography Ischemic Monitoring

“…In addition, technical or skin-electrode impedance problems during the recording may not be identified, potentially leading to loss of data. In contrast to the Holter monitoring system, newer multilead monitoring devices, i.e., S-T segment monitoring based on the 12-lead ECG [23, 24, 25, 26, 27, 28]or QRS and S-T segment monitoring based on VCG [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22], have the option of real-time analysis. Moreover, as compared with multilead monitoring systems, there is an inherent risk of reduced sensitivity of Holter monitoring in detecting myocardial ischemia due to the limited number of exploring electrodes, irrespective of how they are positioned [21, 23].…”

“…An ischemic episode is defined as a transient change of ST-VM and/or STC-Vm >50 µV >1 min from the individual baseline level [14, 16, 17, 18, 19, 20, 22]. A QRS-VD ischemic episode is defined as a transient change >15 µVs from the patient’s baseline level [11, 12, 13, 18].…”

“…A QRS-VD ischemic episode is defined as a transient change >15 µVs from the patient’s baseline level [11, 12, 13, 18]. It has been demonstrated that STC-VM is more sensitive than ST-VM, in particular in relation to the detection of posterior and lateral myocardial ischemia [21, 34].…”

“…The prognostic value of ST-VM and/or STC-VM episodes has been documented in a number of studies [12, 13, 14, 16, 17, 18, 19, 20]. Andersen et al [16]found among 195 patients suspected of having UCS that 23% of those with one or more ST-VM episodes suffered the combined end point of death or AMI/reinfarction within 12 months in contrast to 10% of the patients without ST-VM episodes (p < 0.05; the same figures for a STC-VM discrimination limit of three episodes were found to be 23 versus 9%, p < 0.05).…”

“…More objective techniques for risk assessment of patients have been proposed during the last decades as a supplement to the medical history and examination. These include methods that assess the electrical consequences of UCS, i.e., 12-lead electrocardiogram (ECG) [3, 4], predischarge exercise ECG testing [5, 6], and continuous QRS and S-T segment monitoring [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28]; analyses that assess the myocardial damage, i.e., myocardial biochemical markers, e.g., the troponins [6, 19, 27, 29], and tests that assess the contractile function, i.e., stress echocardiography [30], and myocardial blood flow, i.e., sestamibi SPECT scintigraphy [31]. The method of continuous vectorcardiography ischemic (QRS and S-T segment) monitoring (VCG) is increasingly used in this respect.…”