Intracardiac Electrode Detection of Early or Subendocardial Ischemia*

Abstract

Subendocardial and early transmural ischemia may have significant clinical consequences while manifesting few ECG changes. Catheters were designed to be introduced transvenously into the right ventricle (RV), and coronary sinus (CS) and transarterially into the left ventricle (LV). The intracavitary electrodes were modified so that the electrodes would not contact the endocardium. In twenty-two dogs ninety-eight graded stenoses of the circumflex and left anterior descending coronary arteries were performed while electrograms (EGM) were recorded simultaneously from the intracardiac (IC) electrodes and surface ECG. Of those stenoses resulting in only nonspecific ECG changes, there were specific ischemic changes on 100% of LV, 60% of RV, and 89% of CS electrograms. Of those stenoses which resulted in no ECG change, there were specific ischemic changes in the 9/31 (29%) of LV, 3/31 (10%) of RV, and 6/31 (19%) of CS electrograms. Recognizable patterns of change occur on the intracardiac electrograms in response to both stenosis and reperfusion, earlier than any change on the ECG. Besides being more sensitive, intracardiac electrodes allowed for the detection of ischemia even in the presence of intraventricular conduction defects, strain patterns, and possibly other situations which might otherwise mask ischemic changes on the ECG.

Initial Clinical Results Using Intracardiac Electrogram Monitoring to Detect and Alert Patients During Coronary Plaque Rupture and Ischemia

“…Indeed, in Cases 1 and 4, the surface 12-lead ECG was insensitive to left circumflex coronary artery occlusion. This finding is consistent with prior demonstrations that the ICEG is more sensitive than surface ECG to balloon occlusion during angioplasty (13,14,(17)(18)(19). Further, the real-time quantification available from a selfnormative implanted monitor increases sensitivity compared with that of traditional ECG.…”

Real-Time Detection and Alerting for Acute ST-Segment Elevation Myocardial Ischemia Using an Implantable, High-Fidelity, Intracardiac Electrogram Monitoring System With Long-Range Telemetry in an Ambulatory Porcine Model

“…The rapid evolution of ICEG-detected ST-segment elevation in the current study is consistent with the clinical observations using a temporary right ventricular pacemaker lead during PCI, as reported by Varriale and Niznik (17), Fischell et al (16), and others (19,21,22).…”

“…Previous testing of this concept in patients, using an intracardiac electrogram (ICEG) obtained from a skin electrode on the left upper chest to a temporary (pacemaker) electrode in the right ventricular apex has demonstrated consistent, rapidly evolving, and dramatic ST-segment shifts during balloon occlusion during percutaneous coronary intervention (PCI) in humans (16,17,21,22). Permanently implanted leads have the advantage of being free from ST-segment artifact, muscle noise, transthoracic damping, or concerns about electrode movement over the course of electrocardiogram (ECG) monitoring.…”

Real-time assessment of acute myocardial ischaemia by an intra-thoracic 6-lead ECG: evaluation of a new diagnostic option in the implantable defibrillator†

“…[11][12][13] The key advantage of the IT 6-lead-ECG as described by us 7 and the working groups of Theres et al 9 and Ghuran et al 10 is the heart-surrounding position of the leads in the present ICD generation. Theres et al 9 used a similar study protocol in a smaller patient group and compared the IT-ECG only with the surface ECG leads I, II, and V2.…”