Assessment of myocardial adrenergic innervation in patients with sick sinus syndrome: effect of asynchronous ventricular activation from ventricular apical stimulation.
OBJECTIVE
To investigate ventricular sympathetic innervation in patients with sick sinus syndrome and to detect regional deterioration of adrenergic innervation caused by asynchronous ventricular activation from right ventricular pacing.


METHODS
Prospective controlled study.


METHODS
Tertiary cardiac referral centre.


METHODS
22 patients with sick sinus syndrome and indications for permanent dual chamber pacing; 20 healthy individuals as controls.


METHODS
All patients underwent myocardial imaging with planar and single photon emission computed tomography (SPECT) after an intravenous infusion of 5 mCi 123I-meta-iodobenzylguanidine (123I-MIBG) before and after pacemaker implantation. A SPECT thallium201 myocardial study was done during the same week as the 123I-MIBG study in all patients.


METHODS
The heart to mediastinum (H/M) ratio and washout rate were calculated during the 123I-MIBG study to assess the global cardiac sympathetic activity; the aim of the SPECT study was to investigate the regional distribution of adrenergic innervation.


RESULTS
The H/M ratio was significantly smaller in the patients with sick sinus syndrome than in the controls (p < 0.001). In sick sinus syndrome there were regional adrenergic innervation defects, mostly in the inferior and apical walls. After a medium term pacing period, a redistribution of 123I-MIBG uptake was detected, with deterioration of adrenergic innervation in the inferior, apical, and posterior walls. The thallium201 myocardial perfusion study showed no change after three months of permanent pacing.


CONCLUSIONS
Patients with sick sinus syndrome have global and regional disturbances of the adrenergic innervation of the left ventricular myocardium. These seem to deteriorate as a result of asynchronous electrical activation. The clinical significance of this finding requires further investigation.
Marketou
M E
ME
Cardiology Department, University Hospital of Heraklion, Crete, Greece.
Simantirakis
E N
EN
Prassopoulos
V K
VK
Chrysostomakis
S I
SI
Velidaki
A A
AA
Karkavitsas
N S
NS
Vardas
P E
PE
D019797:3-Iodobenzylguanidine; D000368:Aged; D016022:Case-Control Studies; D015716:Electrocardiography, Ambulatory; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000294:innervation*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000294:innervation; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012804:Sick Sinus Syndrome / Q000000981:diagnostic imaging / Q000473:pathology*; D013564:Sympathetic Nervous System / Q000000981:diagnostic imaging; D013794:Thallium Radioisotopes; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
D019275:Radiopharmaceuticals; D013794:Thallium Radioisotopes; D019797:3-Iodobenzylguanidine