Long-term follow-up of patients from a randomised trial of atrial versus ventricular pacing for sick-sinus syndrome. - Danish Mode Selection Trial


This study compared single-lead atrial pacing to ventricular pacing in patients with sick sinus syndrome.


In patients with sick sinus syndrome, single-chamber, atrial pacing would be associated with lower frequencies of atrial fibrillation, thromboembolism, heart failure, and mortality when comparted to ventricular pacing.

Study Design

Study Design:

Patients Screened: 1052
Patients Enrolled: 255
Mean Follow Up: Mean 5.5 Years
Mean Patient Age: Mean 76
Female: 63

Patient Populations:

Patients were enrolled if they had symptomatic bradycardia with heart rate <50 beats per minute or symptomatic QRS pauses of more than 2 seconds.


1. Atrioventricular block 2. Chronic atrial fibrillation or trial fibrillation >50% of time (2-4 days before implantation) 3. Atrial fibrillation with RR >3 seconds or atrial fibrillation with QRS rate <40 beats/min 4. Blood pressure >250/120 mm Hg 5. Age <50 years 6. Bifasicular bundle branch block 7. Cardiac or major surgery planned 8. Cancer 9. Cerebral disease or stroke within 3 months 10. Wenkebach block with HR <100 beats/min

Primary Endpoints:

The primary endpoints were mortality, atrial fibrillation, first thromboembolism (stroke, peripheral arterial embolism), and severity of heart failure. Atrial fibrillation was diagnosed by 12-lead electrocardiogram at follow-up visit and was defined as chronic if present at 2 vconsecutive follow-up visits. Heart failure was graded according to the New York Heart Association criteria and by the daily dose of diuretics.

Secondary Endpoints:

Pacemaker complications

Drug/Procedures Used:

Patients were randomized to atrial or ventricular pacing with unipolar leads and passive fixation. Screw-in fixation was employed if passive fixation was not successful. Follow-up visits wre obtained at 3 months, 12 months and yearly thereafter.

Concomitant Medications:

If patients developed atrial fibrillation during pacemaker implantation, antiarrhythmic medications were used to terminate the rhythm.

Principal Findings:

Atrial pacing was associated with a decreased rate of all cause mortality and cardiovascular death (relative risk 0.66 [95% CI 0.44-0.99]; p=0.045 and 0.47 [0.27-0.82; p=0.0065 repectively), however in multivariate analysis atrial pacing was associated with less cardiovascular death but not overall mortality. The incidences of atrial fibrillation and chronic atrial fibrillation were also significantly lower atrially paced patients(0.54 [0.33-0.89], p=0.012 and 0.35 [0.16-0.76], p=0.004, respectively). Thromboembolic events were also less frequent in the atrially paced group (0.47 [0.24-0.92], p=0.023). Heart failure was less severe in the atrial group than in the ventricular group (p<0.05). The risk of developing atrioventricular block in the atrial group was approximately 0.6% annually.


Atrial pacing is associated with a significantly lower rate of cardiovascular death, lower rates of atrial fibrillation, fewer thromboembolic complications, reduced heart failure, and a low-risk of atrioventricular block.


1. Andersen HR, Thuesen L, Bagger JP, Vesterlund T, Thomsen PE. Prospective randomised trial of atrial versus ventricular pacing in sick-sinus syndrome.Lancet 1994 Dec 3;344(8936):1523-8 2. Andersen HR, Nielsen JC, Thomsen PE, Thuesen L, Mortensen PT, Vesterlund T, Pedersen AK. Long-term follow-up of patients from a randomised trial of atrial versus ventricular pacing for sick-sinus syndrome. Lancet 1997 Oct 25;350(9086):1210-6.

Keywords: Thromboembolism, Atrioventricular Block, Risk, Multivariate Analysis, Heart Atria, Follow-Up Studies, Sick Sinus Syndrome, Heart Failure, Bradycardia, Heart Rate, Bone Screws

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