Characterization of Ischemia Related Changes in Esophageal Electrocardiography

Background

Heart rhythm disorders frequently occur in the general population and potentially have serious consequences. Atrial fibrillation, the most common atrial arrhythmia, can lead to intracardiac blood clot formation an subsequent embolisation. Esophageal electrocardiography (eECG) provides detailed information about the electrical activity of the atria. Due to the good signal quality, eECG is a promising technique for rhythm monitoring.

Patients undergoing rhythm monitoring may also show signs of other cardiac diseases, particularly coronary artery disease (CAD) due to its high prevalence. It is therefore mandatory to define the ischemic changes in the esophageal ECG.

In CAD atherosclerotic processes narrow the lumen of coronary arteries and may cause exercise-induced ischemia (stable CAD). More importantly, there is also the risk of plaque rupture and subsequent blood clot formation. This cascade can lead to total occlusion of the coronary vessel and myocardial infarction.

Coronary angiography is used to determine the severity of coronary artery stenosis. This simple approach turned out to be useful in clinical routine. However, presence or absence of coronary collaterals is one of the reasons why coronary angiography alone may fail to define the clinical relevance of CAD. Collateral vessels as natural bypasses can grow and act as "backup" blood supply of the myocardial area at risk and can therefore reduce infarct size. The coronary wedge-pressure method is recognized as the scientific and clinical gold standard. Collateralization is an important confounder which also can "mask" ischemic changes on the ECG.

The surface ECG of an important portion of patients undergoing arrhythmia screening also shows signs of myocardial ischemia due to CAD or left ventricular hypertrophy. As with the surface ECG, it is conceivable that ischemic changes occur in the eECG. The characterization of ischemia related changes in eECG is crucial in order to guarantee the proper classification of eECG events. To date, the characterization of such changes is not adequate in order to allow the reliable clinical interpretation of eECG changes.

Objective

• To characterize changes in the esophageal ECG induced by myocardial ischemia due to short-time coronary occlusion.
• To determine the influence of coronary collateral vessels on these changes.

Methods

Patients referred for elective coronary angiography will be randomized to four groups:

• Patients undergoing temporary myocardial ischemia produced by a one-minute balloon occlusion of the proximal left anterior descending (LAD) coronary artery.
• Patients undergoing temporary myocardial ischemia produced by a one-minute balloon occlusion of the proximal left circumflex artery.
• Patients undergoing temporary myocardial ischemia produced by a one-minute balloon occlusion of the proximal right coronary artery.
• Patients undergoing temporary ischemia produced by a one-minute occlusion of the target vessel (the vessel which shows a significant stenosis and accordingly requires a therapeutical intervention).

During the occlusion, collateral flow indexes will be calculated. Simultaneously, surface ECG, esophageal ECG and intracoronary ECG will be registered.

Inclusion criteria

• Patients referred for elective coronary angiography
• Age >/= 18 years
• Written informed consent to participate to this study

Exclusion criteria

• Seve mitral- or aortic valve disease
• Acute coronary infarction
• Known bleeding diathesis
• Systolic blood pressure >200mmHg
• History of operations of the esophagus
• Active disease of the upper respiratory and gastroesophageal tract
• Radiofrequency ablation of atrial fibrillation, less than six weeks ago
• Right and left bundle branch block
• Significant Q-waves in the surface leads as indicators for prior myocardial infarction
• Pregnancy