Abstract
The use of peripheral extracorporeal life support during refractory cardiac arrest sometimes exposes the patient to left ventricular dilatation requiring venting. We report here a simple technique for LV venting by a cannula inserted through right subclavian artery and positioned in the left ventricle.
Keywords: Extracorporeal life support, Left ventricle dilatation, Left ventricle decompression
BACKGROUND
The use of peripheral extracorporeal life support (ECLS) during refractory cardiac arrest causes exposure to left ventricular dilatation, which requires venting. We report here a simple and inexpensive technique for left ventricle (LV) venting using a right subclavian artery approach.
CASE PRESENTATION
A female patient aged 43 years, weight 85 kg, height 1.63 m, suffered cardiac arrest at her home due to myocardial infarction. External cardiac massage was initiated by the family. No-flow time was estimated at 5 min. Coronary angiography led to thrombo-aspiration and implantation of two stents at the ostium of the left anterior descending artery, and of the diagonal branch. An intra-aortic counterpulsation balloon was inserted. The patient's haemodynamic status subsequently deteriorated with LV ejection fraction estimated at 15% by echocardiography. Percutaneous veno-arterial ECLS was initiated with perfusion of the left lower limb. We used a 24-Fr venous cannula (Ref: DFTV024) and a 20-Fr arterial cannula (Ref: DVFM II 020A) (Edwards Lifesciences, Irvine, CA, USA).
The next day, repeat echocardiography showed dilatation of the LV with grade 2/4 mitral valve regurgitation. The aortic valve was tricuspid, with thin cusps and no aortic insufficiency. We then decided to vent the LV.
In our hybrid catheterization laboratory, the right subclavian artery was exposed. A guidewire was introduced through the right subclavian artery to the apex of the LV. The entry orifice was dilated. Over the guide, we introduced a Carmeda-coated cannula, 15 Fr in diameter and 50 cm in length (DLP® Medtronic Bio-Medicus® Cannulae, Carmeda® bonding, ref: 96 600–015, Medtronic, Inc., Minneapolis, MN, USA) with its introducer. The lateral orifices of the cannula were positioned in the LV opposite the mitral valve (Fig. 1). The proximal end of the cannula was connected in a Y-formation to the venous line of the ECLS. Perfusion of the right upper limb was achieved through a 5-Fr sheath, connected to the femoral arterial cannula (Fig. 2). We checked that perfusion was effective by (i) the warmth of the right arm and (ii) finger re-colouration time. Another solution, which we did not use in this case, would be to monitor arterial pressure of the right upper limb by a catheter inserted in the right radial artery.
Figure 1:
Positioning of the left ventricle venting cannula.
Figure 2:
Left: Peripheral extracorporeal life support with both upper and lower limb perfusion. Right: Upper view of the patient showing the left ventricle venting cannula and the upper limb perfusion coming from the arterial cannula inserted through the femoral artery.
During ECLS, overall flow ranged from 4.5 to 4.8 l/min with a venting flow from 1.4 to 2 l/min.
Echocardiography performed the day after surgery showed that the mitral insufficiency had disappeared, and the LV had returned to its normal diameter. Aortic insufficiency due to the passage of the cannula was trivial. At Day 6 post-surgery, LV function had recovered, with an ejection fraction at 35%. The patient was then weaned from ECLS with reconstruction of the right subclavian artery. Unfortunately, the patient presented a postanoxic coma and never regained consciousness. She died 2 months after weaning.
DISCUSSION
Venting of the LV is sometimes required during peripheral ECLS. Dilatation of the LV may be due to several factors: (i) The afterload induced by ECLS on an impaired ventricle; (ii) suboptimal venous return with the right heart recovery; (iii) heavy collateral bronchial flow; and (iv) aortic insufficiency. In our case, there was no aortic insufficiency before LV venting, and insignificant insufficiency after LV venting. Before venting, pump flow ranged between 4.4 and 4.8 l/min for a theoretical flow of 4.6 l/min. To attain the aim of optimizing recovery of the LV, it is necessary to alleviate the LV, as it can hamper vascularization and recovery, and can cause malignant ventricular arrhythmia. Furthermore, elevated LV wall tension leads to pulmonary oedema. LV dilatation causing mitral insufficiency due to annulus dilatation is an infrequent presentation of LV dilatation.
Several methods of LV decompression exist. Two methods are based on the same principle, namely removing blood from the LV to inject it into the aorta. These are the Impella® device (Abiomed, Inc., Danvers, MA, USA) [1, 2] and the PulseCath® device (Intra-Vasc, Groningen, Netherlands) [3]. Both these systems present the advantage of creating a flow in the aortic root, thereby avoiding thrombosis of the aortic root and/or the aortic valve. An alternative is percutaneous insertion through the femoral vein of a cannula to drain the left atrium by the transseptal route. Our experience shows that draining the left atrium, while it avoids pulmonary oedema, has no effect on LV dilatation, except in case of mitral insufficiency. Further alternatives are the placement of transapical [4], left atrium, or left appendage cannula by mini-thoracotomy.
Decompression by means of a Carmeda-treated cannula placed in the LV by the right subclavian route appeared to us to be an attractive solution. The insertion of the cannula is easy in a hybrid cathlab. The flow of the venting line was measured by a specific flow-meter placed on this line. The drainage flow could easily be controlled by partial clamping of the venting line. The procedure should be performed under cardiac echography, in order to determine the right flow, according to the diameter of the LV and the aortic cusps opening. It can sometimes be necessary to temporarily clamp the decompression cannula, at a fixed rhythm, so as to obtain sufficient opening of the aortic valve and washout of the aortic root. If LV function is insufficient to ensure opening of the aortic valve, ad hoc anticoagulation should be performed.
During the weaning phase, this type of venting makes it possible to simultaneously manage the haemodynamic and respiratory issues. Indeed, blood gas analysis performed on the venting cannula directly reflects the LV blood gases. When the LV ejects, arterial saturation of the brain can be assessed by an ear-clip pulse oximeter. For weaning, the venting line is disconnected first.
CONCLUSION
Decompression of the LV using a cannula inserted through the right subclavian artery appears to be an attractive alternative method of LV venting in the context of peripheral circulatory support.
Conflict of interest: none declared.
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