sinus bradycardia has a rate of less than 60 beats per minute.
sinus bradycardia has a rate of less than 60 beats per minute.
which sinus rhythm has a rate of less than 60 beats per minute?
sinus bradycardia
sinus bradycardia









































sinus bradycardia is a sinus rhythm with a rate that is lower than normal. in humans, bradycardia is generally defined to be a rate of under 60 beats per minute.









































section::::signs and symptoms.









































the decreased heart rate can cause a decreased cardiac output resulting in symptoms such as lightheadedness, dizziness, hypotension, vertigo, and syncope. the slow heart rate may also lead to atrial, junctional, or ventricular ectopic rhythms.
sinus bradycardia
the pattern of prepotential or spontaneous depolarization, followed by rapid depolarization and repolarization just described, are seen in the sa node and a few other conductive cells in the heart. since the sa node is the pacemaker, it reaches threshold faster than any other component of the conduction system. it will initiate the impulses spreading to the other conducting cells. the sa node, without nervous or endocrine control, would initiate a heart impulse approximately 80–100 times per minute. although each component of the conduction system is capable of generating its own impulse, the rate progressively slows from the sa node to the purkinje fibers. without the sa node, the av node would generate a heart rate of 40–60 beats per minute. if the av node were blocked, the atrioventricular bundle would fire at a rate of approximately 30–40 impulses per minute. the bundle branches would have an inherent rate of 20–30 impulses per minute, and the purkinje fibers would fire at 15–20 impulses per minute. while a few exceptionally trained aerobic athletes demonstrate resting heart rates in the range of 30–40 beats per minute (the lowest recorded figure is 28 beats per minute for miguel indurain, a cyclist)–for most individuals, rates lower than 50 beats per minute would indicate a condition called bradycardia. depending upon the specific individual, as rates fall much below this level, the heart would be unable to maintain adequate flow of blood to vital tissues, initially resulting in decreasing loss of function across the systems, unconsciousness, and ultimately death.
cardiac physiology