Modification of sinus node function by epicardial laser irradiation in dogs.

Abstract

This study tested the feasibility of neodymium:YAG laser photocoagulation of selected sinus node areas to depress sinus rate responsiveness. In 14 open-chest dogs, origin of the sinus impulse (0 point) was electrically mapped from the epicardium before and during isoproterenol infusion. Epicardial laser photocoagulation was applied to the 0 point observed during isoproterenol infusion and stepwise to remapped new 0 points until a 30±5% decrease in heart rate occurred. Long-term effects were assessed by Holter monitoring and electropharmacologic testing preoperatively and up to 10 weeks or 6 months. Mean (± SEM) percent decreases were observed at 10 weeks in the following parameters: average 24-hour heart rate, 17.4+±5.0%; maximum heart rate on Holter, 30.5+±3.5%; heart rate during pharmacologic autonomic blockade, 32.7±3.5%; and maximum heart rate on isoproterenol, 23.1±4.6% (all p<0.01). Curves with pacemaker recovery time plotted against control cycle length remained unchanged. Holter monitoring did not show excessive bradycardic episodes even after administration of propranolol. In three control dogs (sham operation), sinus node function remained unchanged. Histologic study of the irradiated area showed replacement by inflammatory cells, fibrosis, and cartilage formation with surrounding normal cells and occasional cells resembling pacemakerlike cells at the caudal end of the sinoatrial node. This study suggests that 1) map-guided graded laser photocoagulation of sinus node regions showing earliest activation during catecholamine stimulation successfully limits maximum heart rates without causing significant bradycardia, 2) the effects are long lasting, and 3) the remaining pacemaker behaves like the sinus node. Laser modification of sinus node function could become a form of nonpharmacologic heart rate control in patients with coronary artery disease undergoing surgery and in the syndrome of inappropriate sinus tachycardia. (Circulation 1990;81:350-359) P harmacologic control of excessive sinus tachycardia in humans is occasionally limited by side effects inherent to the drugs used, patient intolerance, or treatment failure related to the nature of the disease.12 Therapeutic options for severe cases of drugresistant sinus tachycardia today include total surgical exclusion of the sinus node region or cryosurgical ablation.34 Both procedures usually result in atrial or Supported by grants from the Heineman Medical Research Center of Charlotte, NC, Inc, and HL-30558-06 from the National Institutes of Health, National Heart, Lung, and Blood Institute, Bethesda, Maryland.Address for correspondence: Laszlo Littmann, MD, Laser and Applied Technologies Laboratory, Carolinas Heart Institute, PO Box 32861, Charlotte, NC 28232.Received April 11, 1989; revision accepted September 13, 1989. atrioventricular junctional escape rhythms and necessitate implantation of a permanent pacemaker. The functional anatomy of the sinus node region in humans and dogs is unique in that it shows widespread distribution and rate differ...

Laser Modification of Sinus Node Function in Dogs

“…We would like to raise awareness about an experimental study we performed almost three decades ago, in which we too employed continuous-wave Nd:YAG laser irradiation for the modification of sinus node function in dogs. 2 There were distinct differences, however, between the study by Weber et al 1 and our study. 2 First, we employed an epicardial rather than endocardial approach.…”

“…2 There were distinct differences, however, between the study by Weber et al 1 and our study. 2 First, we employed an epicardial rather than endocardial approach. Second, in our study, the origin of the sinus impulse (ie, the O-point) was electrically mapped before and during isoproterenol infusion.…”

High‐Density Mapping of the Sinus Node in Humans: Role of Preferential Pathways and the Effect of Remodeling

“…However, no insulated rapidly conducting atrial tissue analogous to that found in the ventricles has been conclusively demonstrated to support the former explanation 6 . Supporting the latter hypothesis, autonomically mediated shifts in activation sites do appear to be linked to the changes in heart rate, 7 although the mechanism by which a stable heart rate is maintained without faster pacemakers dominating is yet to be demonstrated.…”

Structural and Functional Properties of Subsidiary Atrial Pacemakers in a Goat Model of Sinus Node Disease

“…Due to its SAN-like properties, PNA might be an interesting target for attempting the generation of biological atrial pacemakers, which can potentially circumvent specific limitations of electronic pacemakers (Rosen et al, 2004). In fact, in both clinical setting and animal studies, it has been demonstrated that, irrespective of the pathological process, once the SAN has failed, SAP tissue takes over as the leading pacemaker (Randall et al, 1978;Rozanski et al, 1983;Littmann et al, 1990;Kalman et al, 1995;Matsuo et al, 2010).…”