The valve of Vieussens is a frequent cause of obstruction to passage of a catheter in postmortem and in vivo studies. An acute bend in the vein, with or without lodgment in a tributary, is the other common cause. In adults, venous luminal diameter is not a cause of obstruction to the passage of a 7-French catheter in the coronary sinus or proximal GCV.

Postural syncope is a transient loss of consciousness secondary to a reduction in cerebral blood flow and is typically precipitated by standing. It is the commonest cause of recurrent transient loss of consciousness.

No abstract

Familial VVS, inherited in an autosomal dominant manner, may not be rare and has similar features to sporadic VVS. The chromosome 15q26 locus in family A increases the susceptibility to VVS but does not predispose to a particular vasovagal trigger. Linkage analysis in the remaining families established likely genetic heterogeneity.

Programmed upper rate pacing occurred in a patient with a rate-adaptive pacemaker when he was connected to a cardiac monitor in an emergency department. The tachycardia was mistakenly interpreted to be ventricular tachycardia and the patient received multiple DC shocks as well as intravenous amiodarone and sotalol, resulting in severe hemodynamic deterioration. It is important that physicians working in the hospital environment be familiar with this pacemaker-monitor interaction as the problem may be easily rectified by disconnecting the monitor or by reprogramming the pacemaker to a nonrate-adaptive pacing mode.

No abstract

Vasovagal syncope (VVS) is the commonest cause of recurrent syncope and has a high level of morbidity in both young and elderly patients. Diagnosis and treatment are often unsatisfactory despite the fact that syncope has a lifetime cumulative incidence of 35%. A detailed history can often yield an accurate diagnosis in most young patients. Older patients are more likely to present in an atypical manner and although the yield is low, a more comprehensive diagnostic assessment may be needed. It is important to identify patients with low supine systolic blood pressure who are prone to recurrent VVS. These patients represent a distinct subtype of VVS and may respond to a tailored therapeutic approach. Treatment options for VVS are limited because of a paucity of randomized trials. The backbone of therapy is educating the patient, avoiding precipitating factors, maintaining hydration and the application of physical counter-pressure manoeuvres. Drug therapy is rarely warranted; however, fludrocortisone, a-agonists, such as midodrine and dihydroergotamine, and selective serotonin reuptake inhibitors may be helpful in some patients. Permanent cardiac pacing is rarely needed and randomized trials do not support its use.

No abstract