Thoracic sympathetic nuclei ischemia: Effects on lower heart rates following experimentally induced spinal subarachnoid hemorrhage.

BACKGROUND: The neuropathological mechanism of heart rhythm disorders, following spinal cord pathologies, to our knowledge, has not yet been adequately investigated. In this study, the effect of the ischemic neurodegeneration of the thoracic sympathetic nuclei (TSN) on the heart rate (HR) was examined following a spinal subarachnoid hemorrhage (SSAH). METHODS: This study was conducted on 22 rabbits. Five rabbits were used as a control group, five as SHAM, and twelve as a study group. The animals' HRs were recorded via monitoring devices on the first day, and those results were accepted as baseline values. The HRs were remeasured after injecting 0.5 cc of isotonic saline for SHAM and 0.5 cc of autolog arterial blood into the thoracic spinal subarachnoid space at T4-T5 for the study group. After a three-week follow-up with continuous monitoring of their HRs, the rabbit's thoracic spinal cords and stellate ganglia were extracted. The specimens were evaluated by histopathological methods. The densities of degenerated neurons in the TSN and stellate ganglia were compared with the HRs. RESULTS: The mean HRs and mean degenerated neuron density of the TSN and stellate ganglia in control group were 251±18/min, 5±2/mm3, and 3±1/mm3, respectively. The mean HRs and the mean degenerated neuron density of the TSN and stellate ganglia were detected as 242±13/min, 6±2/mm3, and 4±2/mm3 in SHAM (P>0.05 vs. control); 176±19/min, 94±12/mm3, and 28±6/mm3 in the study group (P<0.0001 vs. control and P<0.005 vs. SHAM), respectively. CONCLUSIONS: SAH induced TSN neurodegeneration may have been responsible for low HRs following SSAH. To date this has not been mentioned in the literature.

Relationship between left atrial functions, P-terminal force and interatrial block in chronic haemodialysis patients.

OBJECTIVE: Interatrial block (IAB) connotes a P wave duration ≥ 110 msec on electrocardiography (ECG). P-terminal force corresponds to a biphasic P wave with its terminal negative phase ≥ 40 msec x mm in V1 derivation on ECG. IAB and P-terminal force are closely related parameters and they are accepted as predictors for left atrial dysfunction, left atrial dilatation, atrial fibrillation and strokes. Left atrial functions in chronic haemodialysis patients becomes worse in the course of time because of long standing pressure and volume overload. The aim of this study is to evaluate the relationship between IAB, P-terminal force and left atrial functions. PATIENTS AND METHODS: 68 chronic haemodialysis patients and 60 control subjects were included in the study. Conventional echocardiography and left atrial dynamic functions were measured in all cases. The subjects with IAB and P-terminal force on ECG were identified. RESULTS: Left ventricular size, wall thickness and left atrial diameters were significantly greater in haemodialysis patients than the control group (p < 0.001). 42 (62%) patients had IAB (≥ 110 msec) and 45 (66%) patients had P-terminal force ( ≥ 40 msec x mm) in the haemodialysis group. Left atrial reservoir, conduit and pump functions were significantly lower in the haemodialysis group than the control group (p < 0.001). There was a statistically significant correlation between left atrial functions, IAB (≥ 110 msec) and P-terminal force (≥ 40msec x mm) in all parameters (p < 0.001). CONCLUSIONS: This study showed that decreased left atrial functions in chronic haemodialysis patients are closely correlated with IAB and P-terminal force.

Two cases of very late bare-metal stent thrombosis and literature review.

BACKGROUND: Bare metal stents (BMS) are commonly used in the treatment of coronary artery disease. Very late stent thrombosis (VLST) is a quite rare clinical entity. However, it is a serious complication that often results myocardial infarction or death. Since the stent endothelialization is considered to be completed within 4 weeks after the intervention, VLST is not common with BMS. PATIENTS AND METHODS: The pathogenesis of the VLST is poorly defined. Herein, we report two cases of VLST in which one a 62 year old male patient devoloped VLST of a BMS implanted in the right coronary artery (RCA) and presented inferior myocardial infarction and other a 48 year old male patient devoloped very late thrombosis of a BMS implanted in the RCA and presented inferior myocardial infarction, respectively. CONCLUSIONS: On the basis of these two cases and our review of the current literature we suggest that what can be done to prevent this rare but offending complication. Moreover, in the light of new imaging modalities such as optical coherence tomography (OCT), the pathophysiology of stent thrombosis will be clearly defined and preventive measures will be taken before it occurs.