Heart Dysrhythmias PDF

1/9/24, 1:04 AM herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9a… Introduction Dysrhythmias are disorders of the formation, conduction, or both the formation and conduction of the electrical impulse within the heart. These dis...

1/9/24, 1:04 AM herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9a… Introduction Dysrhythmias are disorders of the formation, conduction, or both the formation and conduction of the electrical impulse within the heart. These disorders can cause disturbances of the heart rate, heart rhythm, or both. Dysrhythmias may initially be evidenced by the hemodynamic effect they cause (e.g., a change in conduction may change the pumping action of the heart and cause decreased blood pressure) and are diagnosed by analyzing the electrocardiographic (ECG) waveform. Their treatment is based on the frequency and severity of symptoms produced. Dysrhythmias are named according to the site of origin of the electrical impulse and the mechanism of formation or conduction involved. Sinus Bradycardia Sinus bradycardia occurs when the SA node creates an impulse at a slower-thannormal rate. Causes include lower metabolic needs (e.g., sleep, athletic training, hypothyroidism), vagal stimulation (e.g., from vomiting, suctioning, severe pain), medications (e.g., calcium channel blockers [e.g., nifedipine, amiodarone], betablockers [e.g., metoprolol]), idiopathic sinus node dysfunction, increased intracranial pressure, and coronary artery disease, especially myocardial infarction (MI) of the inferior wall. Unstable and symptomatic bradycardia is frequently due to hypoxemia. Other possible causes include acute altered mental status (e.g., delirium) and acute decompensated heart failure (Fuster et al., 2017). Sinus bradycardia has the following characteristics (see Fig. 22-6): https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9aojXmGqF3r… 1/6 1/9/24, 1:04 AM herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9a… Ventricular and atrial rate: Less than 60 bpm in the adult Ventricular and atrial rhythm: Regular QRS shape and duration: Usually normal, but may be regularly abnormal P wave: Normal and consistent shape; always in front of the QRS PR interval: Consistent interval between 0.12 and 0.20 seconds P:QRS ratio: 1:1 All characteristics of sinus bradycardia are the same as those of normal sinus rhythm, except for the rate. The patient is assessed to determine the hemodynamic effect and the possible cause of the arrhythmia. If the decrease in heart rate results from stimulation of the vagus nerve, such as with bearing down during defecation or vomiting, attempts are made to prevent further vagal stimulation. If the bradycardia is caused by a medication such as a beta-blocker, the medication may be withheld. If the slow heart rate causes significant hemodynamic changes resulting in shortness of breath, acute alteration of mental status, angina, hypotension, ST-segment changes, or premature ventricular complexes (PVCs), treatment is directed toward increasing the heart rate. Slow heart rate may be due to sinus node dysfunction (previously known as sick sinus syndrome), which has a number of risk factors including increased body mass index, presence of right and left bundle branch block, history of a major cardiovascular event, increased age, and hypertension (Jackson, Rathakrishnan, Campbell, et al., 2017). Tachy-brady syndrome is the term used when bradycardia alternates with tachycardia. Medical Management https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9aojXmGqF3r… 2/6 1/9/24, 1:04 AM herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9a… Management depends on the cause and symptoms. Resolving the causative factors may be the only treatment needed. If the bradycardia produces signs and symptoms of clinical instability (e.g., acute alteration in mental status, chest discomfort, or hypotension), 0.5 mg of atropine may be given rapidly as an intravenous (IV) bolus and repeated every 3 to 5 minutes until a maximum dosage of 3 mg is given. Rarely, if the bradycardia is unresponsive to atropine, emergency transcutaneous pacing can be instituted, or medications, such as dopamine, isoproterenol, or epinephrine, are given (Kusumoto, Schoenfeld, Barrett, et al., 2019. Sinus Tachycardia Sinus tachycardia occurs when the sinus node creates an impulse at a faster-thannormal rate. Causes may include the following: •Physiologic or psychological stress (e.g., acute blood loss, anemia, shock, hypervolemia, hypovolemia, heart failure, pain, hypermetabolic states, fever, exercise, anxiety) •Medications that stimulate the sympathetic response (e.g., catecholamines, aminophylline, atropine), stimulants (e.g., caffeine, nicotine), and illicit drugs (e.g., amphetamines, cocaine, ecstasy) •Enhanced automaticity of the SA node and/or excessive sympathetic tone with reduced parasympathetic tone that is out of proportion to physiologic demands, a condition called inappropriate sinus tachycardia •Autonomic dysfunction, which results in a type of sinus tachycardia referred to as postural orthostatic tachycardia syndrome (POTS). POTS is characterized by tachycardia without hypotension, and by presyncopal symptoms such as palpitations, lightheadedness, weakness, and blurred vision, which occur with sudden posture changes Sinus tachycardia has the following characteristics (see Fig. 22-7): https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9aojXmGqF3r… 3/6 1/9/24, 1:04 AM herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9a… Ventricular and atrial rate: Greater than 100 bpm in the adult, but usually less than 120 bpm Ventricular and atrial rhythm: Regular QRS shape and duration: Usually normal, but may be regularly abnormal P wave: Normal and consistent shape; always in front of the QRS, but may be buried in the preceding T wave PR interval: Consistent interval between 0.12 and 0.20 seconds P:QRS ratio: 1:1 All aspects of sinus tachycardia are the same as those of normal sinus rhythm, except for the rate. Sinus tachycardia does not start or end suddenly (i.e., it is nonparoxysmal). As the heart rate increases, the diastolic filling time decreases, possibly resulting in reduced cardiac output and subsequent symptoms of syncope (fainting) and low blood pressure. If the rapid rate persists and the heart cannot compensate for the decreased ventricular filling, the patient may develop acute pulmonary edema. Medical Management Medical management of sinus tachycardia is determined by the severity of symptoms and directed at identifying and abolishing its cause. Vagal maneuvers, such as carotid sinus massage, gagging, bearing down against a closed glottis (as if having a bowel movement), forceful and sustained coughing, and applying a cold stimulus to the face (such as applying an ice-cold wet towel to the face), or administration of adenosine should be considered to interrupt the tachycardia. If the tachycardia is persistent and causing hemodynamic instability (e.g., acute alteration in mental status, chest discomfort, hypotension), synchronized cardioversion (i.e., electrical current given in synchrony with the patient’s own QRS complex to stop an arrhythmia) is the treatment https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9aojXmGqF3r… 4/6 1/9/24, 1:04 AM herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9a… of choice, if vagal maneuvers and adenosine are unsuccessful or not feasible (see later discussion). IV beta-blockers (Class II antiarrhythmic) and calcium channel blockers (Class IV antiarrhythmic) may also be considered in treating hemodynamically stable sinus tachycardia, although synchronized cardioversion may be used if medications are ineffective or contradicted (Page, Joglar, Caldwell, et al., 2016). Catheter ablation (see later discussion) of the SA node may be used in cases of persistent inappropriate sinus tachycardia unresponsive to other treatments. Treatment for POTS often involves a combination of approaches, with treatment targeted at the underlying problem. For example, patients with hypovolemia may be advised to increase their fluid and sodium intake, or use salt tablets if necessary Sinus Arrhythmia Sinus arrhythmia occurs when the sinus node creates an impulse at an irregular rhythm; the rate usually increases with inspiration and decreases with expiration. Nonrespiratory causes include heart disease and valvular disease, but these are rare. Sinus arrhythmia has the following characteristics (see Fig. 22-8): https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9aojXmGqF3r… 5/6 1/9/24, 1:04 AM herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9a… Ventricular and atrial rate: 60 to 100 bpm in the adult Ventricular and atrial rhythm: Irregular QRS shape and duration: Usually normal, but may be regularly abnormal P wave: Normal and consistent shape; always in front of the QRS PR interval: Consistent interval between 0.12 and 0.20 seconds P:QRS ratio: 1:1 Medical Management Sinus arrhythmia does not cause any significant hemodynamic effect; therefore, it is not typically treated. https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbusjeLUzRyumZIEGwikvZDA89aMIS3TVE3sojJO9aojXmGqF3r… 6/6