Total arterial revascularization is associated with long-term survival benefit in coronary artery bypass grafting: systematic review with meta-analysis

Importance

Total arterial revascularization (TAR), the complete avoidance of saphenous vein grafting (SVG) in coronary artery bypass grafting (CABG), is advocated based on the superior conduit durability and resistance against atherosclerosis. However, the low adoption rate of TAR indicates a high level of controversy.

Objective

To compare long-term survival between TAR and conventional CABG involving SVG.

Data sources

A comprehensive literature search was conducted through digital databases including MEDLINE, Embase, and Cochrane Central Register of Controlled Trials from the inception to May 2021.

Study selection

The inclusion criteria were randomized clinical trials, or propensity-score balanced or multivariable-adjusted observational studies with a sample size of at least 100 patients in each arm, isolated CABG, comparing TAR (SVG=0) vs. non-TAR (SVG≥1), and inclusion of all-cause mortality.

Data extraction and synthesis

Two reviewers performed independent extraction following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Pooled hazard ratios (HR) and 95% confidence intervals (CI) were estimated with random-effect and fixed-effect models using generic inverse variance weighting. Individual patient time-to-event data were reconstructed to create an overall Kaplan-Meier survival function for matched studies. Sensitivity analyses were performed according to the risk of bias, matching status, and source of HR.

Main outcomes and measures

The primary endpoint was all-cause mortality.

Results

A total of 23 studies (100,314 patients), all with a retrospective observational design, were identified. The weighted mean follow-up time was 8.8 years post-operatively. Total arterial revascularization was associated with greater freedom from all-cause mortality than non-TAR (HR, 0.77, 95% CI, 0.71 to 0.84, p<0.001). There was evidence of low heterogeneity (I2=45%) across studies. Low publication bias was observed. Leave-one-out influence analysis and sensitivity analyses produced consistent results. Cochrane Collaboration signaling domains showed no critical risk of bias.

Conclusions and relevance

This meta-analysis found superior late survival associated with total arterial revascularization. Further randomized clinical trials are needed.

Funding Acknowledgement

Type of funding sources: None.

Interpreting diaphragmatic movement with bedside imaging, review article

The diaphragm is the most important muscle of respiration. At equilibrium, the load imposed on the diaphragmatic muscles from transdiaphragmatic pressure balances the force generated by diaphragmatic muscles. However, procedural and nonprocedural thoracic and abdominal conditions may disrupt this equilibrium and impair diaphragmatic function. Diaphragmatic dysfunction is associated with respiratory insufficiency and poor outcome. Therefore, rapid diagnosis and early intervention may be useful. Ultrasound imaging provides quick and accurate bedside assessment of the diaphragm. Various imaging techniques have been suggested, using 2-dimensional and M-mode technology. Diaphragm viewing depends on the degree of robe movement, determined by the angle of incidence of the ultrasound beam and by the direction of probe movement. In this review, we will discuss the function of the diaphragm focusing on clinically important anatomical and physiological properties of the diaphragm. We will review the literature regarding various sonographic techniques for diaphragm assessment. We will also explore the evidence for the role of the tidal displacement of subdiaphragmatic organs as a surrogate for diaphragm movement.

The Effect of the Sitting Upright or ‘Beachchair’ Position on Cerebral Blood Flow during Anaesthesia for Shoulder Surgery

The sitting upright or ‘beachchair’ position is commonly used for shoulder arthroscopic surgery. There is a theoretical concern that anaesthetised patients placed in this posture are at risk of reduced cerebral blood flow (CBF), especially if there is associated hypotension. This study investigated the effect of anaesthetic-induced hypotension on estimated cerebral blood flow in patients placed in the beachchair position for shoulder surgery.

Forty patients were randomised to either sedation (propofol infusion 10 to 20 mg.hour-1, n=20) or general anaesthesia using sub minimum alveolar concentration of sevoflurane (n=20). All patients received an interscalene brachial plexus regional block. Internal carotid artery blood flow was measured using the time averaged velocity of the spectral Doppler waveform, and was then used as an estimate of global CBF. Following a pre-anaesthesia study, measurement of internal carotid artery blood flow was made before and after beachchair positioning, and at five-minute intervals during surgery.

Beachchair positioning during general anaesthesia significantly decreased the mean arterial pressure (34±10 mmHg) compared to sedation (4±2 mmHg, P <0.01), and vasopressor therapy was required more often. However, CBF remained constant in both anaesthetised (P=0.83) and sedated patients (P=0.68) despite beachchair positioning, and the fall in mean arterial pressure in the anaesthetised patients. There was no significant difference in CBF between groups (P=0.91). These findings indicate that in patients in the beachchair position receiving sevoflurane anaesthesia, CBF is maintained when mean arterial pressure is above 70 mmHg, consistent with intact autoregulation.

Lung function following cardiac surgery is not affected by postoperative ventilation time

We investigated the effect of postoperative ventilation time on lung function following cardiac surgery. A prospective observational study of 100 elective patients. Anaesthetic technique and postoperative ventilation times reflected the routine of participating anaesthetists. Group I (n = 29) patients were extubated prior to leaving the operating room, Group II (n = 37) within 8 hours and Group III (n = 28) after 8 hours. Oxygen saturation on air, spirometry and chest x-rays were performed preoperatively and on postoperative days 2, 3 and 4. No demographic differences were detected between groups. There was no mortality, perioperative myocardial infarction or reintubation in any group. Lung function significantly declined following surgery in all groups (p<0.0001) for all endpoints, but was not different between groups. Chest x-ray changes were common in all groups but not significantly different between groups. Immediate extubation does not worsen lung function compared to early or late extubation.

Screening the thoracic aorta for atheroma: a comparison of manual palpation, transesophageal and epiaortic ultrasonography

Accurate detection of atheroma within the thoracic aorta is an important part of most stroke prevention strategies in cardiac surgery. The thoracic aorta was divided into six zones corresponding to sites of surgical manipulation. Zones 1-3, proximal, mid and distal ascending aorta, zones 4-5, proximal and distal arch and zone 6, proximal descending aorta. This study compares the accuracy of atheroma detection by manual palpation, epiaortic (EPI) and transesophageal (TEE) ultrasonography in 70 patients.

RESULTS

Using EPI as the reference method for zones 1-4, 14/70 patients were identified with moderate or severe atheroma. The frequency of atheroma was age related with the youngest at 55 years. Compared with EPI, manual palpation correctly detected moderate or severe atheroma in 7/14 patients (p=0.0058) and TEE in only 4/14 patients (p= 0.0002). For TEE, adequate imaging was only obtained in 41/70 in zone 3 and 30/70 in zone 4. Adequate imaging of zones 5-6 was obtained in all patients using TEE. Of 68 patients with adequate imaging of all zones, 36 had moderate or severe atheroma in zones 5-6. The positive predictive value for zones 1-4 based on atheroma in zones 5-6 was 39%. Of 32 patients with nil or mild atheroma in zones 5-6, only 1 had moderate or severe atheroma in zones 1-4 (negative predictive value 94%).

CONCLUSION

Manual palpation and TEE are inaccurate methods of atheroma detection in zones 1-4. Epiaortic ultrasonography is recommended for all patients undergoing cardiac surgery, although the yield will be low for patients < 50 years of age or if there is nil or mild atheroma detected by TEE in zones 5-6.

Assessment of thoracic aortic atheroma by echocardiography: a new classification and estimation of risk of dislodging atheroma during three surgical techniques

A new classification is described to improve precision of thoracic atheroma reporting. In 68 patients, the thoracic aorta was screened with epiaortic and transesophageal echocardiography. The thoracic aorta is divided into 6 zones corresponding to sites of aortic manipulation. Zones 1-3, proximal, mid and distal ascending aorta, Zones 4-5, proximal and distal arch and Zone 6, proximal descending aorta. Each zone is further sub-divided into anterior, left lateral, posterior and right lateral quadrants. There is a marked increase in moderate and severe atheroma between Zones 1-3 and Zone 4-6 (p<0. 001). There is a difference in atheroma by quadrant with the anterior the most frequent. (p<0.001) Once the grade and location of atheroma was classified, a comparison of the estimation of risk of dislodging atheroma during three surgical methods for care, was performed. Of 50 quadrants of atheroma, the composite arterial pedicle Y graft CABG would manipulate 5, Aortocoronary CABG with single aorta cross clamp, 16, and Aortocoronary CABG with aortic partial occlusion clamp, 21. This classification of 6 zones and 4 quadrants within each zone will increase the precision of atheroma reporting and allow better comparison of stroke reduction interventions.