Image found here.
Check out this recently published study regarding Sjogren's syndrome and heart function:
Clinical Investigative Medicine, 2012 Oct 6;35(5):E303.
Atrial electromechanical delay and diastolic dysfunction in primary Sjögren syndrome.
Akyel A, Tavil Y, Tufan A, Yayla C, Kaya A, Tezcan ME, Ozturk MA, Boyaci B. Etlik Ihtisas Education and Research Hospital, Department of Cardiology, Ankara, Turkey.
PURPOSE: In this study we aimed to investigate myocardial function and atrial electromechanical properties by conventional and tissue doppler echocardiography in patients with primary Sjögren syndrome.
CONCLUSION: Myocardial function is disturbed and there is significant atrial electromechanical delay in patients with primary SS. This study is the first to show altered myocardial function and atrial electromechanical properties in primary SS.
I find the results of this small study (Forty patients with Sjogren's syndrome and 25 age- and sex-matched healthy volunteers) intriguing. However, because of the small population of the study, I would guess that many more studies of similar nature would need to be conducted on a much larger scale to confirm their conclusion.
If you want to learn more about the basic anatomy and physiology of the heart, and specifically electrical conduction aspects of the heart which causes the heart to beat, read this, and this.