Labor syncope

Labor syncope indicates obstruction of the outflow tract of the heart, mainly due to aortic stenosis. This syncope reflects cerebral ischemia caused by the simultaneous expansion of peripheral blood vessels due to the inability to increase cardiac output during labor. Prolonged syncope can cause seizures. Low blood volume and positive inotropic drugs (such as digitalis) can exacerbate outflow tract obstruction in patients with hypertrophic obstructive cardiomyopathy, and sudden syncope may occur. Syncope often occurs immediately after exercise due to reduced venous return, decreased left atrial pressure, and decreased ventricular filling. Arrhythmia may also be a contributing factor. Dysfunction after heart valve replacement may also be the cause. Labor syncope can also cause outflow tract obstruction due to other reasons (such as pulmonary vascular obstruction or pulmonary hypertension due to pulmonary embolism), and insufficient left ventricular filling or pericardial tamponade due to decreased left ventricular compliance, or blocked venous return ( Such as severe pulmonary hypertension or tricuspid valve stenosis, intracardiac myxoma). Myxoma can cause orthostatic syncope due to a pedicled left atrial myxoma that blocks the mitral valve opening. Coughing and urination can cause fainting due to reduced venous return. Syncope can also occur during Valsalva movements. Increased intrathoracic pressure limits venous return, reduces cardiac output, and decreases systemic arterial pressure.

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