New, Virtually Wall-Less Cannulas Designed for Augmented Venous Drainage in Minimally Invasive Cardiac Surgery

Virtually Wall-Less versus Standard Thin-Wall Venous Cannula in the Minimally Invasive Mitral Valve Surgery: Single-Center Experience

Background and Objectives: Minimally invasive cardiac surgery (MICS) has been developing since 1996. Peripheral cannulation is required to perform MICS, and good venous drainage and a bloodless field are crucial for the success of this procedure. We assessed the benefits of using a virtually wall-less cannula in comparison with the standard thin-wall cannula in clinical practice. Materials and Methods: Between January 2021 and December 2022, we evaluated 65 elective patients, who underwent isolated minimally invasive mitral valve surgery. Both the virtually wall-less and the thin-wall cannulas were placed through a surgical cut-down. Patients' characteristics at baseline were similar in the two groups, except for the body surface area (BSA), which was greater in the virtually wall-less group compared to the thin-wall one. In the standard group, the size of the cannula was chosen depending on the patient's BSA, and the choice of the Smartcannula was based on their height. Results: There were no significant differences between the two groups in terms of negative pressure applied, target flow achieved, hemolysis, the need for blood transfusion, and the post-operative increases in liver and renal enzymes. However, in all the patients, the estimated target flow was achieved, thereby showing the better hemodynamic performance of the virtually wall-less cannula, since, in this group, the patients' BSA was significantly greater compared to the thin-wall group. Ultimately, the mean cross-clamp time, as an indirect index of the effectiveness of the venous drainage, is shorter in the virtually wall-less group compared with the thin-wall group. Conclusions: The virtually wall-less cannula should be preferred in minimally invasive mitral valve surgery due to its superior performance in terms of venous drainage compared with the standard thin-wall cannula.

Single-Center Experience With a Self-Expandable Venous Cannula During Minimally Invasive Cardiac Surgery

OBJECTIVE

Venous drainage is often problematic in minimally invasive cardiac surgery (MICS). Here, we describe our experience with a self-expandable stent cannula designed to optimize venous drainage.

METHODS

The smart canula^® was used in 58 consecutive patients undergoing MICS for mitral valve disease (n = 40), left atrial myxoma (n = 3), left ventricular outflow tract obstruction (n = 1), and aortic valve replacement via a right anterior minithoracotomy (n = 14) procedures. The venous cannula was placed under transesophageal echocardiography guidance to reach the superior vena cava. Vacuum-assisted venous drainage (between -20 and -35 mm Hg) was used to reach a target flow index of 2.2 L/min/m² at a core temperature of 34 °C using a goal-directed perfusion strategy aimed at a minimum DO₂ of 272 mL/min/m². Cardiopulmonary bypass (CPB) parameters were recorded, and hemolysis-related parameters were analyzed on postoperative days 1 to 7.

RESULTS

Mean body surface area and median body mass index were 1.9 ± 0.2 m² and 25.2 (23.4, 30.2) kg/m². Mean CPB and median cross-clamping times were 107.7 ± 24.4 min and 64.5 (53, 75.8) min, and median CPB flow during cardioplegic arrest was 4 (3.6, 4.2) L/min (median cardiac index 2.1 [2, 2.2] L/min/m²). Venous drainage was considered sufficient by the surgeon in all cases, and insertion and removal were uncomplicated. Mean SvO₂ during CPB was 80.2% ± 5.5%, and median peak lactate was 10 (8, 14) mg/dL, indicating sufficient perfusion. Mean venous negative drainage pressure during cross-clamping was 27.2 ± 12.3 mm Hg. Platelets dropped by 73.6 ± 37.5 K/µL, lactate dehydrogenase rose by 81.5 (44.3, 140.8) U/L, and leukocytes rose by 3.4 (2.2, 7.2) K/µL on postoperative day 1.

CONCLUSIONS

The venous smart canula^® allows for optimal venous drainage at low negative drainage pressures, facilitating sufficient perfusion in MICS.

Anomalous left hepatic vein to coronary sinus in a patient with atrial septal defect: Minimally invasive approach; technical challenges

Left hepatic vein draining into coronary sinus is a rare systemic vascular anomaly. Its presence is significant when it is associated with other cardiac lesions requiring surgery. We report technical challenges in a case of persistent left superior vena cava and left hepatic vein draining into coronary sinus in an adult with ostium secundum atrial septal defect, which was repaired through minimally invasive approach. The main technical challenge in this case was to achieve adequate venous drainage, which was achieved by vacuum assistance and by manipulating the position of femoral venous cannula. We approached through a right anterolateral thoracotomy and adequate venous drainage was achieved without cannulating left hepatic vein or left superior vena cava.

Design optimization of bidirectional arterial perfusion cannula

Objectives

Determine if shortening the covered section of a self-expanding bidirectional arterial cannula, can enhance retrograde flow and thus reduce the risk of lower limb ischemia.

Methods

Outlet pressure vs flow rate was determined for three cannulas types: a 15F self-expanding bidirectional cannula having a covered section of 90 mm, the same cannula but with a shorter covered section of 60 mm, and a Biomedicus cannula as control. The performances of all the cannulas were compared using a computerized flow-bench with calibrated sensors and a centrifugal pump. Water retrograde flow was determined using a tank timer technique. Anterograde and retrograde flow rate versus outlet pressure were determined at six different pump speed.

Results

For each of the six pump speed, both bidirectional cannulas, 60-mm covered and 90-mm covered respectively, showed higher performance than Biomedicus cannula control, as demonstrated by higher flow rate and lower pressure. We also observed that for the bidirectional cannula with shorter covered section, i.e. 60 mm coverage, provides enhanced performance as compared to a 90-mm coverage. Finally, the flow rate and the corresponding pressure can be consistently measured by our experimental set-up with low variability.

Conclusions

The new configuration of a shorter covered section in a bidirectional self-expanding cannula design, may present an opportunity to overcome lower leg ischemia during extra-corporal life support with long term peripheral cannulation.

Clinical Experience in Minimally Invasive Cardiac Surgery With Virtually Wall-Less Venous Cannulas

OBJECTIVE

Inadequate peripheral venous drainage during minimally invasive cardiac surgery (MICS) is a challenge and cannot always be solved with increased vacuum or increased centrifugal pump speed. The present study was designed to assess the benefit of virtually wall-less transfemoral venous cannulas during MICS.

METHODS

Transfemoral venous cannulation with virtually wall-less cannulas (3/8″ 24F 530-630-mm ST) was performed in 10 consecutive patients (59 ± 10 years, 8 males, 2 females) undergoing MICS for mitral (6), aortic (3), and other (4) procedures (combinations possible). Before transfemoral insertion of wall-less cannulas, a guidewire was positioned in the superior vena cava under echocardiographic control. The wall-less cannula was then fed over the wire and connected to a minimal extracorporeal system. Vacuum assist was used to reach a target flow of 2.4 l/min per m with augmented venous drainage at less than -80 mm Hg.

RESULTS

Wall-less venous cannulas measuring either 630 mm (n = 8) in length or 530 mm (n = 2) were successfully implanted in all patients. For a body size of 173 ± 11 cm and a body weight of 78 ± 26 kg, the calculated body surface area was 1.94 ± 0.32 m. As a result, the estimated target flow was 4.66 ± 0.78 l/min, whereas the achieved flow accounted for 4.98 ± 0.69 l/min (107% of target) at a vacuum level of 21.3 ± 16.4 mm Hg. Excellent exposure and "dry" intracardiac surgical field resulted.

CONCLUSIONS

The performance of virtually wall-less venous cannulas designed for augmented peripheral venous drainage was tested in MICS and provided excellent flows at minimal vacuum levels, confirming an increased performance over traditional thin wall cannulas. Superior results can be expected for routine use.

New, optimized, dual-lumen cannula for veno-venous ECMO

Objective:

The present study was designed to assess in vivo a new, optimized, virtually wall-less, dual-lumen, bi-caval cannula for veno-venous ECMO in comparison to a commercially available cannula.

Methods:

Veno-venous extracorporeal membrane oxygenation (ECMO) was carried out in a bovine study (n=5, bodyweight 75±5kg). Following systemic heparinization, ECMO was established in a trans-jugular fashion through a calibrated 23F orifice, using a new, optimized, virtually wall-less, dual-lumen, bi-caval 24F cannula (Smartcanula LLC, Lausanne, Switzerland) versus a commercially available 23F bi-caval, dual-lumen control cannula (Avalon Elite®, Maquet, Rastatt, Germany) in a veno-venous ECMO setup. Veno-venous ECMO was initiated at 500 revolutions per minute (RPM) and increased by incremental steps of 500 RPM up to 2500 RPM. Catheter outlet pressure, catheter inlet pressure, oxygen saturation and pump flow were recorded at each stage.

Results:

Mean flow accounted for 0.37±0.04 L/min for wall-less versus 0.29± 0.07 L/min for control at 500 RPM, 0.97±0.12 versus 0.67±0.06 at 1000 RPM, 1.60±0.14 versus 1.16±0.08 at 1500 RPM, 2.31±0.13 versus 1.52±0.13 for 2000 RPM and 3.02±0.5 versus 2.11±0.18 (p<0.004). The mean venous suction required was 19±8 mmHg for wall-less versus 20±3 mmHg for control at 500 RPM, 7±3 versus 9±4 for 1000 RPM, -11±10 versus -12±8 at 1500 RPM, -39±15 versus -49±10 for 2000 RPM and -60±28 versus -94±7 for 2500 RPM. The mean venous injection pressure accounted for 29±7 mmHg for wall-less versus 27±5 mmHg for control at 500 RPM, 50±6 versus 61±7 at 1000 RPM, 89±10 versus 99±17 for 1500 RPM, 142±14 versus 161±9 at 2000 RPM and 211±41 versus 252 ±3 for 2500 RPM.

Conclusion:

Compared to the commercially available control cannula, the new, optimized, virtually wall-less, dual-lumen, bi-caval 24F cannula allows for significantly higher blood flows, requires less suction and results in lower injection pressures in vivo.