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Pacemaker syndrome is a disease that represents the clinical consequences of suboptimal atrioventricular (AV) synchrony or AV dyssynchrony, regardless of the pacing mode, after pacemaker implantation. It is an iatrogenic disease—an adverse effect resulting from medical treatment—that is often underdiagnosed.〔 In general, the symptoms of the syndrome are a combination of decreased cardiac output, loss of atrial contribution to ventricular filling, loss of total peripheral resistance response, and nonphysiologic pressure waves.〔 Individuals with a low heart rate prior to pacemaker implantation are more at risk of developing pacemaker syndrome. Normally the first chamber of the heart (atrium) contracts as the second chamber (ventricle) is relaxed, allowing the ventricle to fill before it contracts and pumps blood out of the heart. When the timing between the two chambers goes out of synchronization, less blood is delivered on each beat. Patients who develop pacemaker syndrome may require adjustment of the pacemaker, or fitting of another lead to better coordinate the timing of atrial and ventricular contraction. ==Signs and symptoms== No specific set of criteria has been developed for diagnosis of pacemaker syndrome. Most of the signs and symptoms of pacemaker syndrome are nonspecific, and many are prevalent in the elderly population at baseline. In the lab, pacemaker interrogation plays a crucial role in determining if the pacemaker mode had any contribution to symptoms.〔〔 〕 Symptoms commonly documented in patients history, classified according to etiology:〔〔〔 *Neurological - Dizziness, near syncope, and confusion. *Heart failure - Dyspnea, orthopnea, paroxysmal nocturnal dyspnea, and edema. *Hypotension - Seizure, mental status change, diaphoresis, and signs of orthostatic hypotension and shock. *Low cardiac output - Fatigue, weakness, dyspnea on exertion, lethargy, and lightheadedness. *Hemodynamic - Pulsation in the neck and abdomen, choking sensation, jaw pain, right upper quadrant (RUQ) pain, chest colds, and headache. *Heart rate related - Palpitations associated with arrhythmias In particular, the examiner should look for the following in the physical examination, as these are frequent findings at the time of admission:〔〔〔〔 *Vital signs may reveal hypotension, tachycardia, tachypnea, or low oxygen saturation. *Pulse amplitude may vary, and blood pressure may fluctuate. *Look for neck vein distension and cannon waves in the neck veins. *Lungs may exhibit crackles. *Cardiac examination may reveal regurgitant murmurs and variability of heart sounds. *Liver may be pulsatile, and the RUQ may be tender to palpation. Ascites may be present in severe cases. *The lower extremities may be edematous. *Neurologic examination may reveal confusion, dizziness, or altered mental status. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pacemaker syndrome」の詳細全文を読む スポンサード リンク
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