Cardiovascular Emergencies Study Guide for the CEN

Dysrhythmias

Dysrhythmias are any type of heart rhythm caused by abnormal electrical conduction that deviates from normal sinus rhythm. Some require immediate intervention, while others are more benign or resolve spontaneously or by having the underlying cause addressed.

Tachycardia

Tachycardia is a heart rate that is faster than normal for the patient’s specific age. The normal heart rate range varies by age group:

• infant (up to 1 year)—over 180 bpm
• toddler (1-3 years)—over 140 bpm
• preschool (3-5 years)—over 120 bpm
• school-age (5-12 years)—over 118 bpm
• adolescents (13-18 years)—over 100 bpm
• adults—over 100 bpm

Common types of tachycardia include:

• atrial fibrillation
• atrial flutter
• ventricular tachycardia (stable and unstable)
• ventricular fibrillation
• supraventricular tachycardia
• ventricular fibrillation

Some types of tachycardia, such as sinus tachycardia, which occurs during physical exertion, are considered normal. Tachycardias can be wide complex (with a QRS greater than or equal to 0.12 seconds) or narrow complex (with a QRS less than 0.12 seconds).

Assessment

The defining factor in tachycardia is the patient’s heart rate, which you can recognize by checking their pulse or identifying the rate on a telemetry monitor. Symptoms include chest pain, shortness of breath, and dizziness.

Make sure that you can correctly identify common arrhythmias on the monitor. Obtaining an ECG will allow you to confirm the abnormal rhythm that is occurring. In general, patients with minimal symptoms, a normal level of consciousness, and normal blood pressure are considered stable. Intervention may be needed in such patients, but it can wait for hours or even days. If the patient has a decreased level of consciousness, severe symptoms, or hypotension (systolic blood pressure less than 100 mm Hg), they are considered unstable and require immediate intervention.

Treatment

The intervention varies depending on the specific type of arrhythmia, whether the patient is stable or unstable, and whether an underlying cause is responsible for the arrhythmia. For instance, a patient who has completed a bowel cleanse in preparation for a colonoscopy may have low potassium, which can trigger atrial fibrillation.

If the patient is stable and maintains a normal blood pressure, their potassium can be replaced, which often triggers a return to normal sinus rhythm. In the case of supraventricular tachycardia, vagal maneuvers can often cause the heart rhythm to return to normal sinus rhythm. Vagal maneuvers are actions that stimulate the vagus nerve, like blowing into a syringe, bearing down, or putting an ice pack on the face.

Synchronized cardioversion and specific IV medications can be utilized depending on the type of stable tachycardia that the patient is experiencing. Establishing IV access and continuous telemetry monitoring are crucial, as is an ECG to confirm the patient’s heart rhythm.

In the case of unstable tachycardias, immediate defibrillation is required. Depending on the patient’s level of consciousness and severity of hypotension, you may need to initiate high-quality CPR until you can defibrillate the patient. Sedation is usually provided during the cardioversion but may not be in emergent cases. In the ER setting, you will follow ACLS guidelines for CPR and to determine which intravenous medications will treat the specific arrhythmia.

Other Information

Sometimes heart rhythms such as atrial fibrillation and a-flutter are resistant to cardioversion. If this is the case, treatment with a pacemaker or cardiac ablation may be considered. The patient may also require long-term anticoagulant therapy if their CHADS\(_2\) or CHA\(_2\)DS\(_2\)-VASc score is greater than or equal to 2 (indicating a risk of a stroke).

Premature Ventricular Contraction (PVC)

PVCs are an early beat that occurs in the ventricles. They can be occasional or frequent. Bigeminy occurs when every other heartbeat is an early beat, while trigeminy occurs when every third heartbeat is early and quadgeminy is when it happens with every fourth heartbeat.

Assessment

Many patients are unaware that PVCs have occurred at all and are completely asymptomatic, but others may describe them as heart palpitations. In cases when patients are symptomatic, they may experience:

• light-headedness
• dizziness
• anxiety
• chest pain
• fluttering in their chest
• sensation of their heart skipping a beat

The presence of PVCs can be confirmed by ECG or close observation of a telemetry monitor.

Treatment

If PVCs occur only occasionally, and the patient is asymptomatic, treatment may not be required. In cases where they occur more frequently and/or the patient is symptomatic, the first line of treatment is beta blockers and/or calcium channel blockers. If the PVCs do not resolve with oral medication, the next line of treatment is a cardiac ablation. Occasional PVCs are not harmful to the heart, but in the long run, frequent PVCs can induce cardiomyopathy, which will often resolve when the PVCs are controlled.

Ventricular Fibrillation

Ventricular fibrillation is a non-perfusing tachycardia that is fatal within minutes if it is not resolved. It is an extremely rapid (over 300 bpm), irregular ventricular rhythm with no atrial activity noted on the monitor. It is treated with high-quality CPR and defibrillation.

Assessment

With ventricular fibrillation, respirations and pulses will be absent. The patient will be unconscious or will become unconscious within seconds of the onset of ventricular fibrillation. It is confirmed by analysis of the telemetry monitor. Ventricular fibrillation will look like a toddler drew on the telemetry monitor with a crayon. It’s impossible to measure a QRS complex, and the rhythm is extremely irregular. Obtaining a 12-lead ECG to confirm would unnecessarily delay care and decrease the patient’s chance of a positive outcome.

Treatment

Ventricular fibrillation is a shockable rhythm. In an adult patient, CPR should be initiated immediately in a 30:2 ratio of chest compressions and respirations. Emergency defibrillation will hopefully return the patient to a perfusing rhythm, even if it is not normal.

One mg of epinephrine should be administered every three to five minutes via IV push (as long as you can establish IV access; intraosseous access may be needed if a peripheral IV can’t be obtained). If epinephrine is ineffective, the next round of medication should be 300 mg of amiodarone via IV push, with a 150 mg second dose via IV push if the first dose is ineffective. Any other causes, such as electrolyte imbalances or cardiac dysfunction, should also be identified and treated promptly to prevent the recurrence of ventricular fibrillation.

Ventricular Tachycardia

Ventricular tachycardia is a wide-complex tachycardia that is more than three PVCs in a row. The average rate is 100 to 200 beats per minute. It can be stable or unstable. Stable ventricular tachycardia is a perfusable rhythm. When ventricular tachycardia is unstable, the dysrhythmia causes ineffective beats that prevent adequate perfusion and can rapidly cause the patient to lose consciousness. Regardless of whether it is stable or unstable, rapid intervention is always needed.

Assessment

Evaluate the patient’s level of consciousness. Check to see whether their pulse is palpable and frequently obtain vital signs to monitor for hypotension. In the conscious (stable) patient with a palpable pulse, symptoms can include:

• chest pain
• dizziness
• shortness of breath
• the sensation that the heart is racing

If the patient is stable, analyze the patient’s telemetry monitor to measure the width of the QRS complex; the rhythm should also appear regular. The P wave may or may not be present and is often not identifiable even if it is present.

Treatment

If the patient is stable and the rhythm appears regular and monomorphic (remaining the same shape), treatment involves synchronized cardioversion used in conjunction with the administration of 6 mg of adenosine via rapid IV push, followed by a 12 mg second dose via rapid IV push if required.

In the case of unstable ventricular tachycardia, the protocol is the same as ventricular fibrillation. CPR should begin immediately. Emergency defibrillation is needed, along with 1 mg of epinephrine via IV push every three to five minutes through a previously established IV access. If epinephrine and defibrillation are ineffective, the next course of action is to administer 300 mg of amiodarone via IV push, with a second dose of 150 mg if necessary. Any underlying causes of the ventricular tachycardia should also be addressed.

Bradycardia

Bradycardia is an abnormally slow heart rate. The specific definition of bradycardia varies by age:

• infant (up to 12 months)—less than 100 bpm
• toddler (1-3 years)—less than 98 bpm
• preschool (3-5 years)—less than 80 bpm
• school-age (5-12 years)—less than 75 bpm
• adolescents (13-18 years)—less than 60 bpm
• adults—less than 60 bpm

In some instances, bradycardia is a benign occurrence. Athletic individuals often have an exceptionally low resting heart rate and are completely asymptomatic. Common types of bradycardia include:

• sinus bradycardia
• sinus pause (also known as sinus arrest)
• sick sinus syndrome
• tachy-brady syndrome
• heart block (first-degree, second-degree [Mobitz type 1 and Mobitz type 2], and third-degree or complete heart block)

Symptoms include:

• light-headedness
• dizziness
• shortness of breath
• activity intolerance
• fatigue
• fainting
• hypotension
• chest pain

Assessment

Assess the patient’s level of consciousness and check their pulse to see if it is palpable, along with other vital signs. Ask the patient if they are experiencing any of the symptoms listed above. Obtain an ECG and analyze it to determine the specific bradycardia that the patient is experiencing. This knowledge will guide the treatment plan for the patient. Treatment is not usually necessary unless the heart rate is less than 50 bpm in adults or less than 60 bpm in children.

Treatment

In the asymptomatic patient, the only necessary treatment is monitoring. If the patient is symptomatic or hypotensive, 1 mg of atropine may be administered every three to five minutes via IV push. A dopamine infusion at 5 to 20 mcg/kg/min or epinephrine infusion at 2 to 10 mcg/min can be initiated if the patient fails to respond to atropine. If the patient is unresponsive to medication, initiate transcutaneous pacing to increase the heart rate. This can be extremely uncomfortable for the patient who is aware and should only be used on a short-term basis.

Some medications may cause bradycardia, such as beta blockers, and should be stopped or reduced if this occurs. Hypoxia can also result in bradycardia, especially in pediatric patients; ensure that the patient is receiving adequate oxygenation. In more severe cases of bradycardia, such as sick sinus syndrome or a complete heart block, the patient may require the installation of a permanent pacemaker to regulate their heart rhythm.