Vectorcardiographic changes during laparoscopic cholecystectomy may mimic signs of myocardial ischaemia.

Background: Laparoscopic surgery involves the use of intra-abdominal carbon dioxide insufflation (pneumoperitoneum). The increased intra-abdominal pressure causes marked haemodynamic changes, which may influence electrocardiographic monitoring. The aim of the present study was to elucidate the influence of pneumoperitoneum on vectorcardiographic recordings.

Methods: Vectorcardiographic changes (QRS vector difference = QRS-VD, QRS loop area, QRS magnitude, ST vector magnitude, spatial ST vector change) were recorded continuously applying computerized vectorcardiography in 12 anaesthetised cardiovascularly healthy patients, scheduled for laparoscopic cholecystectomy. Measurements were made before and during pneumoperitoneum in three different body positions (supine, Trendelenburg and reversed Trendelenburg), also employing transesophageal echocardiography and invasive blood pressure monitoring.

Results: Pneumoperitoneum significantly increased QRS-VD, in parallel with an enlargement in loop area and magnitude. The magnitude was significantly increased in the transversal and frontal planes and there was a tendency to increase the magnitude in the sagittal plane. The increase in QRS-VD reached levels previously associated with the development of myocardial ischaemia in patients with coronary artery disease. The ST-variables were not changed by the pneumoperitoneum. The positional changes also influenced QRS-VD significantly.

Conclusions: When computerized vectorcardiography is used for ischaemia monitoring during pneumoperitoneum, the ST-variables seem reliable. However, vectorcardiographic QRS-changes should be interpreted with caution, as the QRS alterations found during pneumoperitoneum mimic the changes seen during myocardial ischaemia.