Role of His-Bundle Pacing: Reliability and Potential to Avoid Ventricular Dyssynchrony
F. ZANON, E. BARACCA, S. AGGIO, G. BOARETTO, G. PASTORE, P. ZONZIN
Increasing clinical evidence shows that conventional right ventricular pacing is detrimental to left ventricular function. Recent studies in canines [1]
showed that right ventricular apical (RVA) pacing causes abnormal contrac- tion patterns due to abnormal activation of the left ventricle during RVA pacing compared to normal sinus rhythm. Moreover, these studies gave evi- dence that sustained RVA pacing is associated with histological and structur- al changes that cause left ventricular function to deteriorate. In humans, short- and long-term studies [2, 3] have confirmed the adverse effects of RVA pacing.
A theoretical pacing system that could preserve the normal Purkinje acti- vation should be considered the ideal pacing approach, because the ventricu- lar dyssynchrony would be prevented and the normal activation pattern maintained. However, the traditional pacing tools do not allow an easy approach to the His bundle, and therefore few clinical reports of this pacing mode exist in the literature.
Deshmukh et al. [4, 5] reported the results of direct His-bundle pacing (DHBP) in patients with chronic heart failure and atrial fibrillation who were candidates for ablate-and-pace strategy because of a rapid and pharma- cologically uncontrolled ventricular rate. According to Deshmukh et al., the criteria for verification of the DHBP were the following: (1) recording of His bundle potential with the permanent pacing lead; (2) pace-ventricular inter- val equal to His-ventricular interval ± 15 ms; (3) paced QRS morphology and duration equal to the intrinsic QRS in all 12 ECG leads.
Twelve out of 18 patients in the first study and 39 out of 54 patients in the second study were successfully paced. In a long-term follow-up (42 months) the
Division of Cardiology, General Hospital, Rovigo, Italy
mean NYHA class improved from 3.5 to 2.2 and the ejection fraction increased from 0.23 ± 0.11 to 0.33 ± 0.15. In these studies by Deshmukh et al. the total procedure time was 3.7 ± 1.6 h and a standard screw-in lead (helix 1.5 mm) with modified J-shaped stylet was used to reach the His bundle.
Vázquez et al. [6] attempted DHBP in 12 patients without structural heart disease selected for AV nodal ablation due to uncontrolled paroxysmal atrial fibrillation or for pacemaker implantation because of supra-His conduction disturbances with a normal conduction system. DHBP was successfully achieved in 8 out of 12 patients. Acute and 3-month electrical performances were acceptable and the authors reported a procedure time of 192 min using an approach similar to that of Deshmukh et al.
DHBP is really difficult to achieve with a standard lead with a modified stylet, extending implant time and causing recurrent acute dislodgements.
The tools for biventricular stimulation, designed to facilitate the insertion of leads into the coronary sinus and from there to the lateral distal cardiac vein, suggested the idea that new active-fixation leads guided by steerable catheters could allow right ventricular selective sites to be reached.
The first dedicated tool is the Medtronic SelectSecure system, composed by a steerable catheter (SelectSite – Model C304, Medtronic Inc.) and a 4.1-Fr no stylet, active fixation, bipolar, steroid-eluting lead (Model 3830, Medtronic Inc.). Recently, we started using this new pacing approach in our centre.
DHBP was attempted in 25 patients (17 male, mean age 77 ± 8 years) with standard pacemaker indication and a narrow QRS. All patients underwent implantation using the SelectSecure system. DHBP was achieved in 23 patients (92%); two patients were paced in the His area, but the QRS mor- phology and duration under pacing were different from the native ones.
In DHBP pacing, the acute pacing threshold was 2.4 ± 1.2 V at a pulse width of 0.5 ms, whereas sensed potentials were 3.0 ± 2.0 mV. No major complications were observed.
In conclusion, our preliminary experience with this new tool shows that DHBP is feasible. However, future studies will be necessary to confirm the real benefits of this new pacing technique.
References
1. Amitani S, Miyahara K, Somara H et al (1999) Experimental His-bundle pacing:
histopathological and electrophysiological examination. Pacing Clin Electrophysiol 22[Pt. I]:562–566
2. Gomes JA, Damato AN, Akhtar N et al (1977) Ventricular septal motion and left ventricular dimensions during abnormal ventricular activation. Am J Cardiol 39:641–650
306 F. Zanon et al.
3. Tse H, Lau CP (1997) Long term effects of right ventricular pacing on myocardial perfusion and function. J Am Coll Cardiol 29:744–749
4. Deshmukh P, Casavant D, Romannyshyn M et al (2000) Permanent, direct His- bundle pacing – a novel approach to cardiac pacing in patients with normal His- Purkinje activation. Circulation 101:869–877
5. Deshmukh P, Romannyshyn M (2004) Direct His-bundle pacing: present and futu- re. Pacing Clin Electrophysiol 27[Pt. II]:862–870
6. Vázquez P, Pichardo R, Gamero J et al (2001) Estimulación permanente del haz de His tras ablación medianteradiofrecuencia del nodo auriculoventricular en pacien- tes con trastorno de la conducción suprahisiano. Rev Esp Cardiol 54:1385–1393
307 Role of His-Bundle Pacing: Reliability and Potential to Avoid Ventricular Dyssynchrony
