Vectorcardiographic changes as predictors of cardiac complications during major vascular surgery.

OBJECTIVE: To elucidate the relation of changes in computerized vectorcardiographic trend parameters indicating perioperative myocardial ischemia with perioperative cardiac complications. DESIGN: Prospective clinical study. SETTING: A single university hospital. PARTICIPANTS: Thirty-eight patients undergoing elective abdominal aortic surgery. INTERVENTIONS: Computerized vectorcardiography recorded during surgery and for 48 hours postoperatively. MEASUREMENTS AND MAIN RESULTS: Vectorcardiographic spatial alterations in the QRS complex (QRS-VD) and absolute (ST-VM) and spatial (STC-VM) ST-segment changes, previously used indicators of myocardial ischemia, were analyzed and related to the cardiac events detected clinically. In five patients with clearly ischemic (cardiac death, myocardial infarction, recurrent ischemia) and eight patients with possibly ischemic (congestive heart failure, arrhythmia) perioperative cardiac events, ST-VM and STC-VM were significantly increased intraoperatively. Postoperatively, these differences remained, but QRS-VD were also significantly increased. Intraoperative and postoperative changes indicating ischemia were strongly related (r = 0.83). The signs of ischemia were most pronounced during the postoperative 12 to 36 hours. The presence of 60 minutes of signs of ischemia during 2 hours revealed high sensitivity (85%), specificity (80%), and positive (69%) and negative (91%) predictive values for subsequent cardiac events. Traditional vector loop analysis showed signs of non-Q-wave infarctions in six patients, whereas only three of these were detected using standard clinical methods. CONCLUSIONS: Vectorcardiographic signs of myocardial ischemia were significantly increased intraoperatively, but most pronounced postoperatively in the patients subsequently suffering cardiac events. The changes could be related to the individual cardiac morbidity with acceptable precision. Thus, continuous vectorcardiographic monitoring may be beneficial for patients at risk of developing perioperative ischemia.

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.

Comparison of electrocardiograms recorded with standard leads and derived from the vectorcardiographic frank leads in high risk patients.

Dynamic vectorcardiography (VCG) is increasingly employed for ischaemia monitoring with the use of a computerized method for recording and on-line analysis by the calculation of trend parameters. To elucidate how well the derived electrocardiogram (dECG), calculated from the VCG, compares with the simultaneously registered standard ECG (sECG), dECGs from 17 postoperative cardiac-risk patients and 36 subjects with acute myocardial infarction (AMI) were compared to sECGs, both quantitatively in leads II, III, V2 and V5 and qualitatively. Despite small, but some significant differences, mainly in the amplitudes of precordial leads, the qualitative interpretation by two independent cardiologists showed good agreement between the methods (kappa = 0.72 and 0.67, respectively) for the diagnosis of AMI/ischaemia. The dECG seems to be reliable and can be used clinically in these groups of patients during VCG recordings.

Computerized vectorcardiography for improved perioperative cardiac monitoring in vascular surgery.

BACKGROUND: Postoperative cardiac complications occur frequently after noncardiac operations in high-risk patients. Routine cardiac monitoring is usually done by electrocardiographic (ECG) methods. The present analysis shows that computerized vectorcardiography (VCG) is superior to traditional ECG monitoring in predicting postoperative cardiac complications. STUDY DESIGN: Thirty-eight patients scheduled for abdominal aortic operations were monitored intraoperatively and for 48 hours postoperatively using VCG. These data were analyzed in a blinded fashion, and compared to cardiac outcome and regularly calculated 12-lead ECGs. RESULTS: Thirteen patients suffered from cardiac events: myocardial infarction (n = 3), cardiac death (n = 1), recurrent myocardial ischemia (n = 1), arrhythmias (n = 2), congestive heart failure (n = 2), and arrhythmias combined with congestive heart failure (n = 4). Thirty of 38 patients had ischemia recorded on their VCG, including all 13 patients with cardiac events. Only seven of the 13 patients had ischemic changes on the V5-lead alone and ten on the three leads II, V4, V5, yielding a sensitivity of 54 percent (V5), 77 percent (II, V4, V5) and 100 percent (VCG). Signs of ischemia appeared 400 +/- 690 (mean plus or minus standard deviation) minutes earlier (median 78 minutes, with a range of zero to 2,284 minutes), and never later on the VCG compared to the three leads II, V4, V5. CONCLUSIONS: Vectorcardiography in this risk group shows increased sensitivity in predicting perioperative cardiac complications and earlier ischemia detection than the most sensitive scalar leads. Vectorcardiography substantially improves the possibility of earlier intervention, potentially reducing the incidence of postoperative cardiac complications.

Effects of posture and pneumoperitoneum during anaesthesia on the indices of left ventricular filling.

BACKGROUND: Laparoscopic surgery requires the use of pneumoperitoneum (PP). When combined with positional changes, pneumoperitoneum may cause marked circulatory alterations. METHODS: Eight anaesthetized cardiovascularly healthy patients, scheduled for laparoscopic cholecystectomy, were studied before and during pneumoperitoneum in three different postures (supine, Trendelenburg and reversed Trendelenburg), employing transesophageal echocardiography and pulmonary artery pressure monitoring. RESULTS: PP significantly increased end-diastolic area (EDA) and pulmonary capillary wedge pressure (PCWP) irrespective of posture. PCWP was significantly influenced by postural changes, whereas EDA was not. Further, changes in EDA and PCWP covaried during the investigation, but showed no linear correlation. Systolic function, measured as end-systolic area (ESA) and fractional area shortening (FAS), was not altered. Diastolic function, as assessed by the velocity rate of the transmitral flow during the early filling phase (E) and the atrial contraction (A), showed no change of the E/A ratio, whereas after the induction of PP there was a significant reduction of the E component. CONCLUSIONS: In cardiovascularly healthy patients, the left ventricular volume is increased during pneumoperitoneum. Further, changes in invasive pressure determinations (PCWP) do not correlate linearly with changes in volume indices of left ventricular filling (EDA).

Minimal influence of anaesthesia and abdominal surgery on computerized vectorcardiography recordings.

Myocardial infarction still represents a major cause of morbidity and mortality following surgical procedures. Continuous computerized on-line vector-ECG has previously been shown to be useful in the detection of myocardial ischaemia, in acute myocardial infarction and unstable angina pectoris and for ischaemia monitoring after PTCA procedures. This method was presently tested for the possible influence of anaesthesia and surgery during cholecystectomy under general anaesthesia (n = 9), and during inguinal hernia repairs using a spinal block (n = 5). The patients had no history, symptoms or signs of ischaemic heart disease. Analyses of vectorcardiographic changes were made in relation to predefined standardized anaesthetic and surgical procedures, all of which potentially could influence the vector-ECG. Three vectorcardiographic trendparameters were studied: QRS-vector difference, ST-vector magnitude and ST-change vector magnitude. The overall vectorcardiographic changes were minimal and smaller than vectorcardiographic changes previously reported during myocardial ischaemia and infarction. Since anaesthetic and surgical procedures per se had only minor effects on the vector ECG recordings, it is concluded that continuous computerized on-line vectorcardiography will not be skewed by these procedures. Hence, vectorcardiography has the potential of becoming a new monitor for the detection of perioperative myocardial ischaemia.

Haemodynamic effects of pneumoperitoneum and the influence of posture during anaesthesia for laparoscopic surgery.

The laparoscopic operating technique is being applied increasingly to a variety of intra-abdominal operations. Intra-abdominal gas insufflation, i.e. pneumoperitoneum (PP), is then used to allow surgical access. The haemodynamic effects of PP in combination with different body positions have not been fully examined. Eleven patients without signs of cardiopulmonary disease were studied before and during laparoscopic cholecystectomy under propofol-fentanyl anaesthesia with controlled ventilation. Swan-Ganz and radial arterial catheterization were used to determine haemodynamic data in the horizontal position, with a 15-20 degree head-down tilt and a 15-20 degree head-up tilt. The measurements were repeated after insufflation of carbon dioxide to an intraabdominal pressure of 11-13 mmHg, as well as during surgery. The ventricular filling pressures of the heart were strictly dependent on body position. PP in the horizontal position increased pulmonary capillary wedge pressure by 32% (P < 0.01), central venous pressure by 58% (P < 0.01), and mean arterial pressure by 39% (P < 0.01). When PP was combined with a head-down tilt, there was a further increase in filling pressures by approximately 40% (P < 0.01), while the reduction in filling pressures during the head-up tilt was counteracted by PP. During PP with a head-up tilt, the filling pressures did not differ from those in the horizontal position without PP. CI showed a certain dependency on filling pressures. It is concluded that PP causes signs of elevated preload and afterload. The combination of PP and a head-up tilt is associated only with signs of an elevated afterload.(ABSTRACT TRUNCATED AT 250 WORDS)