Upgrading From Right Ventricular to Biventricular Pacing: When, Why, and How?

When, Why, and How?

R. C

, G. P

Introduction

The incidence of conduction delay in patients with congestive heart failure is approximately 30% [1], and patients with left-bundle-branch block (LBBB) have a worse survival rate than those with heart failure alone [2]. Ventricular dyssynchrony results in regional motion abnormalities of the left ventricular wall that produce a deterioration of cardiac performance.

Right ventricular apical pacing induces a left ventricular conduction pat- tern similar to LBBB, with a QRS vector directed upward and posteriorly. On echocardiography, chronic right ventricular apical pacing produces geomet- ric changes that appear similar to those associated with intrinsic LBBB:

shortening of ventricular filling time, reduction of ventricular d

/d

, and a prolonged duration of mitral regurgitation with detrimental effects on sys- tolic and diastolic function [3]. Some reports [4, 5] have suggested that car- diac asynchrony due to LBBB is greater than dyssynchrony due to right ven- tricular pacing, because a larger portion of the myocardium is prematurely activated.

Cardiac resynchronisation, in which biventricular pacing reduces the intraventricular dyssynchrony of the left ventricle, is a new therapeutic option for patients who have drug-refractory end-stage heart failure [6, 7].

Many controlled prospective trials have show n that this therapeutic approach provides clinical and haemodynamic benefits in patients with advanced heart failure, severe left ventricular dysfunction, and ventricular asynchrony [8, 9]. The role of right ventricular apical pacing in treating patients with heart conditions is unclear, as is whether upgrading to biven-

U.L.S.S. 10 ‘Veneto Orientale’, Unità Operativa Cardiologica, Portogruaro (Venice), Italy

tricular pacing in these patients would provide clinical and haemodynamic improvement. In this article the impact of cardiac resynchronisation therapy in patients with permanent right ventricular pacing and advanced heart fail- ure is assessed.

Evidence of Negative Effects Deriving from Right Ventricular Apical Pacing

Several recent studies evidenced deleterious effects deriving from chronic right ventricular apical pacing. The Canadian Trial of Physiologic Pacing (CTOPP) [10] was a multicentric randomised study that compared VVI pac- ing mode with AAI and DDD mode, considered as ‘physiologic’ pacing. In this trial, no differences were observed in terms of mortality and hospitalisa- tions for patients with heart failure, but right ventricular pacing seemed to provoke a detrimental effect on left ventricular systolic function.

The Danish Study [11], conducted by Nielsen, compared AAI to DDD pac- ing in patients with sick sinus syndrome and confirmed these results. The investigators found an increase in the size of the atrium and a reduced ejec- tion fraction in patients with dual-chamber pacing with a high percentage of stimulation. These negative effects were more evident in patients with sys- tolic dysfunction and/or with a previous episode of congestive heart failure.

The MOST trial [12], which attempted to identify the best pacing mode in patients with sick sinus syndrome, compared AAI to DDD pacing. No bene- fits regarding mortality and cerebral ischaemic accidents were found, but in the group with ventricular pacing there was a worsening of quality of life associated with an increased risk of hospitalisation for heart failure. Sweeney [13] analysed a subgroup of patients with a narrow QRS at baseline and found a close correlation between percentage of right ventricular pacing and haemodynamic and arrhythmic events. Patients with a cumulative right ven- tricular pacing > 40% had an increased risk of hospitalisation for heart fail- ure associated with an increased recurrence of atrial fibrillation.

Similar results were observed in the DAVID study [14], in which patients with a dual-chamber ICD with continuous right ventricular pacing had increased mortality (10.1% vs 6.5%) and more hospitalisations (22,6% vs 13,3%) than those with a single-chamber ICD. The MADIT II trial [15], which assessed primary prevention of ICD in patients with previous myocar- dial infarction and severe left ventricular dysfunction, also showed that fre- quency of hospitalisation for heart failure was higher in patients with ICD- DDD with constant right ventricular pacing.

All these studies underline that right ventricular pacing is not a ‘physio-

logic’ stimulation and it may have negative effects on cardiac performance

due to the development of abnormal motion in the septal, apical, and inferi- or walls as well as of cardiac dyssynchrony deriving from LBBB [16].

Impairments of left ventricular systolic and diastolic function have been demonstrated echocardiographically also in young patients after long-term right ventricular pacing.

Clinical and Haemodynamic Effects of Upgrading from Right Ventricular Apical Pacing to Biventricular Pacing

Very few reports have investigated the potential benefits of upgrading from right ventricular apical pacing to biventricular pacing. Such studies have been limited to patients who were treated with right ventricular pacing in the setting of chronic atrial fibrillation and previous AV junction ablation.

Leon et al. [17] assessed the impact of biventricular pacing in 20 consecutive patients with severe left ventricular dysfunction, advanced heart failure symptoms, chronic atrial fibrillation, and permanent pacing because of prior AV node ablation. They demonstrated significant improvements in NYHA functional class, increased left ventricular ejection fraction, and decreased end-systolic diameters associated with a reduction of hospitalisations. In a randomised single-blind study, Leclercq [18] evaluated patients with advanced heart failure and atrial fibrillation with a slow ventricular rate.

Patients underwent either biventricular pacing programmed in crossover with a period of right ventricular pacing mode or biventricular pacing.

Patients programmed to biventricular pacing showed a significant improve-

ment in exercise tolerance; a reduction in the number of hospitalisations was

also observed. Recently, another study [19] assessed in a long-term follow up

(20 ± 19 months) the effects of upgrading on 16 consecutive patients with

chronic atrial fibrillation, prior AV node ablation, and permanent right ven-

tricular apical pacing. The 14 patients surviving after 6 months evidenced

an amelioration of NYHA class, a reduction of cardiothoracic ratio and

mitral regurgitation, and an increased ejection fraction. Our experience on

upgrading patients with right apical ventricular pacing and heart failure

(NYHA III–IV; ejection fraction < 35%), consists of 28 patients, 43% paced

for sick sinus syndrome and 57% for atrio-ventricular conduction distur-

bances. Before and after upgrading, the patients underwent clinical and

echocardiographic examinations. The results after a 26 ± 9-month follow-

up period demonstrated important clinical improvement in functional class

(NYHA = 1.8 vs 3.2) and a reduction in the number of hospitalisations (0.4

vs 2.4). Similarly, haemodynamic benefits were evidenced with respect to

end-diastolic volume and mitral regurgitation area reduction and enhanced

ejection fraction. The same results were obtained in a comparison of the

upgraded patients with a similar group of patients recommended for cardiac resynchronisation therapy. The implanting procedure was simplified by the presence of stable previously inserted leads. In the major of our patients, we cannulate the coronary sinus directly with the lead until the lateral or pos- terolateral vein, without the use of contrasting iodine agents, and with a very short procedure time.

Discussion

Cardiac resynchronisation therapy improves heart failure symptoms in

patients with LBBB and severe reduction of left ventricular systolic function

[8, 9]. While the effects of upgrading from right ventricular to biventricular

pacing in patients with congestive heart failure have been analysed in only a

few studies, the initial results are highly encouraging. Thus, this procedure

seems to be safe and feasible; procedural success is estimated to be 90–92%,

with a low percentage of complications [20]. Many studies have found that

chronic right ventricular pacing induces desynchronisation, which could

worsen ventricular function and accelerate the progression of heart disease

[21, 22]. Why do some patients develop cardiac heart failure after ‘ablate and

pace’ procedure? In patients with heart failure, in whom symptoms persist in

spite of ventricular rate control, one explanation could be that correcting the

tachycardia and irregular cardiac cycles is insufficient to reverse the evolu-

tion of the underlying heart disease, and that the benefits deriving from AV

node ablation are counterbalanced by the deleterious effects of right ventric-

ular apical pacing [23]. In patients treated with AV junction ablation, it is

often observed that initial well-being is followed by a re-appearance or

recurrence of heart failure symptoms [24]. This implies that the natural evo-

lution of the underlying heart disease is accelerated by the detrimental effect

of long-term right ventricular pacing – a consequence that is maximised in

patients with reduced ventricular performance. In our study we also

observed detrimental effects of right ventricular apical pacing on systolic

function. Before pacemaker implantation, 80% of the patients presented with

moderate left ventricular dysfunction (ejection fraction = 0.42 ± 0.08) and

NYHA I-II. After 24 months of right ventricular pacing, almost 50% of the

patients showed a worsening of congestive heart failure symptoms associat-

ed with severe left ventricular dysfunction. In three patients, the procedure

of upgrading to biventricular pacing became necessary very early (after 3

months). This occurrence led the suggestion that right ventricular apical

pacing associated with initial left ventricular dysfunction seems to worsen

ventricular performance, accelerating progression of heart disease.

Conclusions

Patients with right ventricular pacing and heart failure may be candidates for resynchronisation therapy with the upgrading to biventricular pacing.

The procedure has been shown to be simple and safe. In addition, the results of the above-mentioned studies are encouraging and show that upgraded patients may profit from a better quality of life. However, the life expectancy of these patients remains to be investigated.

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