Leadless pacemaker implantation using halo-shape technique in a severe dextroscoliosis octogenarian

Abstract

The halo-shape technique (HST) is an emerging approach for implanting a leadless pacemaker in scoliosis patients in recent years. Severe scoliosis and humpback made it challenging to push the tip of the delivery catheter towards the ventricular septum using the conventional gooseneck-shape technique. The feasibility and safety of the use of HST in an octogenarian with severe dextroscoliosis and humpback have not been well-assessed. Here, we report a case of high-degree atrioventricular block octogenarian with severe dextroscoliosis and humpback who successfully received a leadless pacemaker implantation using HST. Procedure-related complications were not observed, and the electrical parameters were stable at 6-month follow-up.

Recently, a second generation (Micra AV, Medtronic, Minneapolis, MN) of leadless pacemakers, which functions in VDD mode using a three-axis accelerometer to detect atrial contraction, has been introduced and could be an alternative when ventricular pacing is required [1]. Micra AV, capable of atrioventricular (AV) synchronous pacing, extended the indications to patients with AV block (AVB) and preserved sinus node function [1]. However, in patients with severe skeletal deformities, leadless pacemaker implantations are sometimes challenging [2]. The halo-shape technique (HST) is an emerging approach for implanting a leadless pacemaker in scoliosis patients in recent years [3]. The feasibility and safety of the use of HST in octogenarians with severe scoliosis and humpback have not been well-assessed. This study aimed to present a case where HST was achieved in a dextroscoliosis octogenarian with high-degree AV block and discuss the potential feasibility and safety of this technique for future study.

An 82-year-old hypertensive female weighing 60 kg was referred to the clinic for worsening of palpitation, which lasted for more than 2 months. Physical examination findings were normal apart from severe dextroscoliosis, humpback and bradycardia. The electrocardiogram (ECG) revealed a preserved sinus node function, high-degree AVB and RBBB shape with QRS duration of 160 ms (Fig. 1 Upper). The echocardiogram showed normal anatomy, and normal heart function. Left atrium diameter (74 ml; normal range < 70 ml) enlarged mild. The left ventricular end-diastolic and end-systolic diameters (LVEDD and LVESD), left ventricular ejection fraction (LVEF) were 51, 33 mm, and 60%, respectively. Mild tricuspid regurgitation without abnormal valve anatomy, ventricular function, or pulmonary artery pressure is present. A prospective chest and abdomen CT routine scan revealed a severe dextroscoliosis.

Fig. 1

Twelve-lead electrocardiograms pre-procedure and post-procedure. Upper, Preoperative ECG showed a high-degree AVB and RBBB with QRS duration of 160ms. Below, Postoperative ECG showed a paced ECG with QRS duration of 160 ms

Fig. 2

X-ray images of cardiovascular configuration. Left, Inferior vena cava (IVC) venogram showing IVC or guide wire (white arrows) quite torturous and the spine severe dextroscoliosis (black arrows) in the antero-posterior view. Middle, Attaining a halo-catheter shape of the delivery catheter (white arrows) in left anterior oblique 40-degree. Right, Deployment of the leadless pacemaker in antero-posterior view (white arrow)

The blood reports were entered in Table 1. NT-proBNP was high (1200pg/ml). The other values (TNI, K⁺, GPT and GOT) were normal.

Table 1 Blood reports before implantation

After ruling out reversibility and other causes, the patient presented for pacemaker implantation. Finally, the decision to implant Micra AV and to publish all images, clinical data was made after sufficient discussion and written informed consent was obtained from the patient. A temporary pacing lead was placed in right ventricle (RV) for the treatment of intra-operative bradyarrthymias. Micra AV was implanted by skilled doctors as previously described [4]. Summarily, right common femoral venous access was created and dilated. After insertion of the Micra delivery sheath, a bolus injection of unfractionated heparin was given according to their body weight (500 IU per 10 kg). The leadless device was then advanced to RV. The delivery catheter was withdrawn slowly, rotated clockwise, and then pushed gently to achieve a stable septal location. The position of the device was assessed using the 2 standard fluoroscopic views: right anterior oblique (RAO), left anterior oblique (LAO)

Of note, in this patient, inferior vena cava (IVC) venogram show it was quite torturous (Fig. 2 left), and the tip of delivery catheter could not be directed towards the ventricular septum due to the alteration of orientation of right atrium and ventricle, but it could be directed toward the infero-basal portion (Fig. 2 middle). It is difficult to shape the catheter into a gooseneck-shape, on the contrary, a halo-catheter shape (Fig. 2 middle) could be attained.

In the end, the leadless pacemaker was successfully deployed at that site without any complications (Fig. 2 right), and good device parameters were achieved (sensing, 5 mV; pacing threshold, 0.5 V/ 0.24ms; impedance, 600 ohms). Postoperative ECG showed a paced wave with QRS duration of 160 ms (Fig. 1 below).

No procedure-related complications occurred during the perioperative period and follow-up. At 6-month post procedure, interrogation showed good device parameters. Echocardiography demonstrated that the electrode was positioned at the sub-endocardium of RV septum, and tricuspid regurgitation was mild.

The present case is rare because of his severe dextroscoliosis and humpback. Dextroscoliosis makes your spine curve to the right. It’s the opposite of levoscoliosis, and will give your spine a curve like a backward “C” or a circle with the left side missing. Due to severe tortuous inferior vena cava and transposition of the heart secondary to scoliosis, an impediment to successful implantation of Micra may be present [5].

Severe dextroscoliosis made it difficult, even impossible to push the tip of the delivery catheter towards the ventricular septum, to say nothing of attaining gooseneck-shape. The halo-shape technique is an emerging approach for delivering a leadless pacemaker in scoliosis patients in recent years [3]. Halo-shaped tip section has a preformed curve which can be positioned around the tricuspid annulus. Using HST, the catheter tip could be directed toward the infero-basal portion of the right ventricular and attained halo-catheter shape. The Micra could be successfully deployed at that site. At 6-month post-procedure, the patient was thriving. The patient’s heart function was stable with stable LVEDD and LVEF.

This case reported the application of HST in an octogenarian with severe scoliosis and humpback, and highlighted some of the limitations in the current iteration of Micra deployment technology and demonstrates the possible need for HST with extended reach for varying patient anatomies.

Conclusions

The Micra implantation using HST technique is technically feasible in an octogenarian with severe dextroscoliosis and humpback. A preprocedural anatomical assessment may help to predict the implantability of Micra.