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

Aim In the presence of coronary artery disease, implantable cardioverter-defibrillators (ICD) are used effectively for treating life-threatening tachyarrhythmias. Continuous monitoring of myocardial ischaemia would provide a new diagnostic option in future ICD generations. Methods and results In 22 selected patients undergoing coronary angioplasty, percutaneous transluminal coronary angioplasty (PTCA), three electrodes, similar to those used in the ICD, were inserted aiming to create six intra-thoracic ECG (IT-ECG) leads according to Einthoven and Goldberger. In total, 27 PTCA were conducted. The diagnostic efficacy for ischaemia assessment was compared with the surface ECG. The IT-ECG proved to be more sensitive than conventional ECG in early and overall ischaemia assessment. At 30 s of coronary artery occlusion, ischaemic ST-segment alterations (� 0.25 mV) were present in the IT-ECG 2.3 times more often (23 vs. 10/27 PTCA attempts, P , 0.01) and at 90 s 1.4 times more often compared with conventional ECG leads (18 vs. 26/27, P , 0.05). Intra-thoracic Einthoven 2 (SVC þ RVA vs. ICD-housing) and Goldberger 3 (SVC þ ICD-housing vs. RVA) had the highest sensitivity (88/85%). Using � 4 IT-ECG, ischaemia monitoring was independent of severity and site of origin. IT-ECG signals showed double ST-T signal amplitude (4.19+ 0.6 vs. 2.15+ 0.3 mV, ratio: 1.95, P , 0.01) at a QRS/ST amplitude ratio similar in the two ECG techniques. Conclusion This study provides strong evidence that the ICD-based IT 6-lead ECG would provide a new and efficient means of assessing a patient’s daily ischaemic burden.