Sinus Dysrhythmias Flashcards
What is the pathophysiology of sinus tachycardia?
Sympathetic nervous system stimulation or vagal (parasympathetic) inhibition results in an increased rate of SA node discharge, which increases the heart rate. When the rate of SA node discharge is more than 100 beats/min, the rhythm is called sinus tachycardia. From age 10 years to adulthood, the heart rate normally does not exceed 100 beats/min except in response to activity and then usually does not exceed 160 beats/min. Rarely does the heart rate reach 180 beats/min.
What does it when a patient is sinus tachycardiac?
Sinus tachycardia initially increases cardiac output and blood pressure. However, continued increases in heart rate decrease coronary perfusion time, diastolic filling time, and coronary perfusion pressure while increasing myocardial oxygen demand.
In what instances is increased sympathetic stimulation a normal response?
Increased sympathetic stimulation is a normal response to physical activity but may also be caused by anxiety, pain, stress, fever, anemia, hypoxemia, and hyperthyroidism. Drugs such as epinephrine, atropine, caffeine, alcohol, nicotine, cocaine, aminophylline, and thyroid medications may also increase the heart rate.
In what instances is sinus tachycardia a compensatory response?
In some cases, sinus tachycardia is a compensatory response to decreased cardiac output or blood pressure, as occurs in dehydration, hypovolemic shock, myocardial infarction (MI), infection, and heart failure. Assess patients for signs and symptoms of hypovolemia and dehydration, including increased pulse rate, decreased urinary output, decreased blood pressure, and dry skin and mucous membranes.
What is the desired outcome for a patient experiencing sinus tachycardia?
The desired outcome is to decrease the heart rate to normal levels by treating the underlying cause. Remind the patient to remain on bedrest if the tachycardia is causing hypotension or weakness. Teach the patient to avoid substances that increase cardiac rate, including caffeine, alcohol, and nicotine. Help patients develop stress-management strategies or refer the patient to a mental health professional.
What would the nurse assess for in a patient with sinus tachycardia?
For patients with sinus tachycardia, assess for fatigue, weakness, shortness of breath, orthopnea, decreased oxygen saturation, increased pulse rate, and decreased blood pressure. Also assess for restlessness and anxiety from decreased cerebral perfusion and for decreased urine output from impaired renal perfusion. The patient may also have anginal pain and palpitations. The ECG pattern may show T-wave inversion or ST-segment elevation or depression in response to myocardial ischemia.
What is the pathophysiology of sinus bradycardia?
The stimuli slow the heart rate and decrease the speed of conduction through the heart. When the sinus node discharge rate is less than 60 beats/min, the rhythm is called sinus bradycardia. Sinus bradycardia increases coronary perfusion time, but it may decrease coronary perfusion pressure. However, myocardial oxygen demand is decreased. Well-conditioned athletes with bradycardia have a hypereffective heart in which the strong heart muscle provides an adequate stroke volume and a low heart rate to achieve a normal cardiac output.
What can cause sinus bradycardia?
Excessive vagal (parasympathetic) stimulation to the heart causes a decreased rate of sinus node discharge. It may result from carotid sinus massage, vomiting, suctioning, Valsalva maneuvers (e.g., bearing down for a bowel movement or gagging), ocular pressure, or pain. Increased parasympathetic stimuli may also result from hypoxia, inferior wall MI, and the administration of drugs such as beta-adrenergic blocking agents, calcium channel blockers, and digoxin. Lyme disease, electrolyte disturbances, neurologic disorders, and hypothyroidism may also cause bradycardia.
What should the nurse assess for in a patient with sinus bradycardia?
The patient with sinus bradycardia may be asymptomatic except for the decreased pulse rate. In many cases, the cause of sinus bradycardia is unknown. Assess the electronic health record (EHR) to determine if the patient is receiving medications that slow the conduction through the SA or AV node. Assess the patient for:
- Syncope (“blackouts” or fainting)
- Dizziness and weakness
- Confusion
- Hypotension
- Diaphoresis (excessive sweating)
- Shortness of breath
- Chest pain
What are interventions that can be done for a patient who is sinus bradycardiac?
- If the patient is stable, treatment includes identification and treatment of the underlying cause. If the patient has any of these symptoms and the underlying cause cannot be determined, the treatment is to administer drug therapy with intravenous atropine, increase intravascular volume via IV fluids, and apply oxygen if oxygen saturation is below 94% or the patient is short of air.
- Drugs suspected of causing the bradycardia are discontinued. If beta-blocker overdose is suspected, administration of glucagon may help by increasing the heart rate and blood pressure.
- If the heart rate does not increase sufficiently, prepare for transcutaneous or transvenous pacing to increase the heart rate. If treatment of the underlying cause does not restore normal sinus rhythm, the patient will require permanent pacemaker implantation.
What is temporary pacing for sinus bradycardia?
Temporary pacing is a nonsurgical intervention that provides a timed electrical stimulus to the heart when either the impulse initiation or the conduction system of the heart is defective. The electrical stimulus then spreads throughout the heart to depolarize the cells, which should be followed by contraction and cardiac output. Electrical stimuli may be delivered to the right atrium or right ventricle (single-chamber pacemakers) or to both (dual-chamber pacemakers).
Temporary pacing is used for patients with symptomatic bradydysrhythmias who do not respond to atropine or for patients with asystole. There are two types of temporary pacing: transcutaneous and transvenous.
What is and what type of pacing is transcutaneous pacing?
It is a type of temporary pacing.
- Transcutaneous pacing is accomplished through the application of two large external electrodes. The electrodes are attached to an external pulse generator. The generator emits electrical pulses, which are transmitted through the electrodes and then transcutaneously to stimulate ventricular depolarization when the patient’s heart rate is slower than the rate set on the pacemaker. Transcutaneous pacing is used as an emergency measure to provide demand ventricular pacing in a profoundly bradycardic or asystolic patient until invasive pacing can be used or the patient’s heart rate returns to normal. This method of pacing is painful and may require administration of pain and sedative medications for the patient to tolerate the therapy. Transcutaneous pacing is used only as a temporary measure to maintain heart rate and perfusion until a more permanent method of pacing is used.
What is and what type of pacing is transvenous pacing?
Transvenous pacing is a type of temporary pacing.
- A temporary transvenous system can be inserted in an emergency as a bridge until a permanent pacemaker can be inserted. This system consists of an external battery-operated pulse generator and pacing electrodes, or lead wire. The wire attaches to the generator on one end and is threaded to the right ventricle via the subclavian or femoral vein.
How do pacemaker systems work?
In pacemaker systems, electrical pulses, or stimuli, are emitted from the negative terminal of the generator, flow through a lead wire, and stimulate the cardiac cells to depolarize. The current seeks ground by returning through the other lead wire to the positive terminal of the generator, thus completing a circuit. The intensity of electrical current is set by selecting the appropriate current output, measured in milliamperes.
What are the two major modes of pacing?
The two major modes of pacing are synchronous (demand) pacing and asynchronous (fixed-rate) pacing.
