Familial combined sinus node and atrioventricular conduction dysfunctions

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Stroke complicating congenital sick sinus syndrome

We report the case of a patient with congenital sick sinus syndrome complicated by atrial fibrillation and embolic stroke 23 years after the initial diagnosis, at the age of 34 years. Treatment with a dual-chamber pacemaker and oral anticoagulation were initiated; further follow-up was uneventful but pacemaker diagnostics constantly documented asymptomatic recurrences of paroxysmal atrial fibrillation.

Pacemaker Channels and Sinus Node Arrhythmia

Cardiac pacemaker activity is regulated by at least five different classes of ion channels and by the opposing influence of sympathetic and parasympathetic stimulation. Inactivation of several genes, including a subunit coding for the potassium channel activated by the muscarinic receptor, I(KACh); the calcium channel, I(Ca,); and the hyperpolarization-activated channel, I(f), results in sinus node arrhythmia. Inactivation of the gene for the hyperpolarization-activated, cyclic nucleotide-gated channel isoform HCN2 or HCN4 and the use of pacemaker channel blockers show that (a) HCN2 prevents the diastolic membrane potential from becoming too negative, (b) HCN4 is the major channel mediating sympathetic stimulation of the pacemaker activity, and (3) complete blockage of the I(f) current is compatible with slow sinus node rhythm.

Familial sick sinus syndrome with atrioventricular conduction disturbance

A family with sick sinus syndrome is presented: a mother and her 2 daughters affected with sinus node dysfunction. Electrophysiological studies revealed abnormal atrioventricular conduction in the 2 daughters. All 3 individuals were implanted with a permanent pacemaker to relieve their symptoms. Endomyocardial biopsy from the right ventricle of one daughter showed disarrangement, degeneration, myocyte necrosis and interstitial fibrosis suggestive of myocardial disease.