Regular Rate Tachycardia Case File

Regular Rate Tachycardia Case File

Eugene C. Toy, MD, Barry C. Simon, MD, Terrence H. Liu, MD, MHP, Katrin Y. Takenaka, MD, Adam J. Rosh, MD, MS

Case 4

A 25-year-old man presents to the emergency department (ED) with palpitations and lightheadedness. These symptoms started acutely about 1 hour prior to arrival while he was watching television. The patient does not have any chest pain or shortness of breath. He also denies any recent fever, upper respiratory symptoms, and hemoptysis. He does not have any significant past medical history or family history. He is not taking any medications, does not smoke, and has never used any illicit drugs.

On examination, his temperature is 98.2°F, his blood pressure is 88/46 mm Hg, his heart rate 186 beats per minute, respiratory rate is 22 breaths per minute, and oxygen saturation is 97% on room air. He is mildly anxious but otherwise in no acute distress. He does not have any jugular venous distention. His lungs are clear to auscultation, and his heart sounds are regular without any murmurs, rubs, or gallops. There is no lower extremity edema, and peripheral pulses are equal in all four extremities. The cardiac monitor reveals a regular rhythm with narrow-QRS complexes at a rate of 180 to190 beats per minute.

⯈ What is the most likely diagnosis?

⯈ What is the most appropriate next step?

ANSWER TO CASE 4:

Regular Rate Tachycardia

Summary: This is a 25-year-old man with acute onset of palpitations and dizziness. He is hypotensive and has a narrow-QRS complex tachycardia at a rate of 180 to 190 beats per minute.

• Most likely diagnosis: Supraventricular tachycardia.
• Most appropriate next step: Obtain IV access and a 12-lead ECG. Prepare for synchronized cardioversion of this unstable patient with a tachyarrhythmia.

ANALYSIS

Objectives

1. Learn the differential diagnosis for regular rate tachycardias.
2. Recognize the clinical signs and symptoms to differentiate between stable and unstable patients with regular rate tachycardias.
3. Understand the diagnostic and therapeutic approach to regular rate tachycardias.

Considerations

When evaluating a patient with a tachyarrhythmia, assessment of the patient’s stability is paramount. Unstable patients will require immediate synchronized cardioversion. Stable patients may be able to be managed medically. All patients will require continuous cardiac monitoring, intravenous (IV) access, and a 12-lead ECG. Regular rate tachycardias include several types of supraventricular tachycardia and ventricular tachycardia (Table 4–1). As a general rule, narrow-QRS complex tachycardias arise from above the ventricles while wide-QRS complex ones may be supraventricular or ventricular in origin.

Approach To:

Regular Rate Tachycardia

CLINICAL APPROACH

Patients with tachyarrhythmias may present with a host of complaints including palpitations, fatigue, and weakness. Other symptoms may suggest a component of hypoperfusion (dizziness, near syncope, or syncope) or cardiac ischemia (chest pain, dyspnea). If the patient is stable enough for a complete history to be performed, the history should also include information about the time and circumstances surrounding symptom onset, duration of symptoms, past medical history (eg, history of coronary artery disease, congestive heart failure, dysrhythmia, valvular disease, thyroid disease), current medications (including herbal or homeopathic regimens, over-the-counter medicines, and illicit drugs), and family history (eg, sudden cardiac death, dysrhythmia, other types of heart disease).

The physical examination will initially focus on assessing the patient’s stability and adequacy of the ABCs. Any evidence of hypotension, pulmonary edema, acutely altered mental status, or ischemic chest pain indicates that the patient is unstable and treatment must be initiated immediately (see treatment section below). Once the patient is stabilized, a complete head-to-toe examination can be performed. Special consideration should be given to the cardiovascular and lung components of the examination: auscultating heart sounds for gallops, murmurs, and rubs; palpating for the point of maximal impulse and any heaves; inspecting for jugular venous distention; listening for any rales or other findings of volume overload; assessing the quality of peripheral pulses. The examination may also reveal clues regarding underlying causes of tachycardia (eg, pale mucous membranes with anemia; thyromegaly or goiter with thyrotoxicosis, barrel chest or nail clubbing with chronic lung disease).

A 12-lead ECG is ostensibly the most useful diagnostic test when evaluating a patient with a tachyarrhythmia (Figures 4–1 and 4–2). These arrhythmias may be separated into regular and irregular rate tachycardias as well as narrow- or wide- QRS (>0.12 s) complex (see Table 4–1). As a general rule, narrow-QRS complex tachycardias arise from above the ventricles while wide-QRS complex ones may be supraventricular or ventricular in origin.

Table 4–2 lists the distinguishing ECG characteristics of the various types of regular rate tachycardias.

Ventricular tachycardia (VT) may be difficult to differentiate from a supraventricular tachycardia (SVT) with aberrant conduction. Certain factors favor VT, including age ≥50, history of coronary artery disease or congestive heart failure, history of VT, atrioventricular dissociation, fusion beats, QRS >0.14 second, extreme left axis deviation, and precordial concordance (QRS complexes either all positive or all negative). In contrast, age ≤35, history of SVT, preceding ectopic P waves with QRS complexes, QRS <0.14 second, normal or almost normal axis, and slowing or cessation of the arrhythmia with vagal maneuvers suggest SVT with aberrancy. If the provider cannot distinguish between VT and SVT with aberrancy with certainty, the patient should be treated as if VT is present.

Figure 4–1. Atrial flutter with 2:1 conduction.

Chest x-rays may be useful to assess for chamber enlargement, cardiomegaly, pulmonary congestion or edema. A basic metabolic panel can rule out electrolyte abnormalities that predispose to tachyarrhythmias (eg, hypokalemia, hypocalcemia, hypomagnesemia). If the clinical scenario is suggestive, thyroid function studies (for hyperthyroidism), drug levels (eg, digoxin), or urine drug screen (for cocaine, methamphetamines, other stimulants) may be warranted.

Treatment

All patients with tachyarrhythmias require monitoring of vital signs (blood pressure, oxygen saturation, continuous cardiac monitoring) and IV access. If the patient is

Figure 4–2. Ventricular tachycardia. Note arrows pointing to P waves and are completely dissociated

from the QRS complexes.

hypoxic or in respiratory distress, supplemental oxygen and airway support are indicated. If the patient is unstable (as evidenced by hypotension, pulmonary edema, altered mental status, or ischemic chest pain), synchronized cardioversion should be performed immediately. If time allows, sedation should be given prior to cardioversion.

In stable patients, a 12-lead ECG should be obtained, and medical therapy can be initiated. Potential interventions for regular narrow-complex tachyarrhythmias include vagal maneuvers (such as carotid massage and Valsalva), adenosine, β-blockers, and calcium-channel blockers. Although vagal maneuvers will not terminate tachyarrhythmias that do not involve the AV node, they may slow the rate enough to unmask the underlying rhythm abnormality. Stable patients with regular wide-complex tachycardias may benefit from amiodarone, procainamide, or sotalol. Second-line therapy for stable patients with monomorphic VT is lidocaine.

COMPREHENSION QUESTIONS

4.1 A 22-year-old baseball player comes into the ED complaining of 12 hours of intermittent chest pain and a pounding heartbeat. He denies a history of trauma. On examination, he is tachycardic. Which of the following is the best next step?

A. Synchronized cardioversion

B. Valsalva maneuver

C. Discharge home and follow up within the next 48 hours

D. Obtain an ECG

4.2 A 52-year-old healthy jogger is brought to the ED following a syncopal episode. A diagnosis of ventricular tachycardia is made, and the patient is cardioverted. She states that she has had prior episodes of VT lasting less than 30 seconds each. What is the most appropriate treatment?

A. Likely no further therapy is needed.

B. Amiodarone

C. β-blocker

D. Procainamide

4.3 All of these are AV nodal blocking maneuvers except:

A. Diving reflex

B. Carotid massage

C. Valsalva maneuver

D. Holding one’s breath at the end of expiration

4.4 An 87-year-old woman presents with chest pain and shortness of breath. The 12-lead ECG shows a “sawtooth” pattern with a heart rate of 150 beats per minute. What is the most likely diagnosis?

A. AVNRT

B. VT

C. Atrial flutter

D. Atrial fibrillation with rapid ventricular rate

4.5 A 37-year-old woman presents with chest pain after smoking crack 2 hours ago. What are you most likely to see on the ECG?

A. Sinus tachycardia

B. SVT

C. VT

D. Atrial fibrillation

ANSWERS

4.1 D. One must characterize the rhythm before initiating treatment.

4.2 A. Nonsustained VT is by definition a self-terminating event, and therefore usually no specific treatment is indicated. Rather, treatment is directed at any existing heart condition.

4.3 D. AV nodal blocking maneuvers include Valsalva, diving reflex, and carotid massage. They act through the parasympathetic nervous system. If an SVT involves the AV node, slowing conduction through the node can terminate the arrhythmia. SVTs that do not involve the AV node will not usually be terminated by AV nodal blocking maneuvers. However, these maneuvers may still cause a transient AV block and unmask the underlying rhythm abnormality.

4.4 C. Classically atrial flutter presents with a saw tooth pattern on ECG. The rate of 150 bpm denotes that it’s likely a 2:1 conduction block.

4.5 A. The most common regular rate tachycardia is sinus tachycardia.

CLINICAL PEARLS

⯈ Regular rate tachycardias include several types of supraventricular tachycardia and ventricular tachycardia. As a general rule, narrow-QRS complex tachycardias arise from above the ventricles while wide-QRS complex ones may be supraventricular or ventricular in origin.

⯈ If the patient is unstable (as evidenced by hypotension, pulmonary edema, altered mental status, or ischemic chest pain), synchronized cardioversion should be performed immediately. In stable patients, a 12-lead ECG should be obtained, and medical therapy can be initiated.

⯈ If the provider cannot distinguish between VT and SVT with aberrancy with certainty, the patient should be treated as if VT is present.

⯈ Always order an ECG in a patient with suspected tachyarrhythmia.

References

Baerman JM, Morady F, DiCarlo LA Jr, de Buitleir M. Differentiation of ventricular tachycardia from supraventricular tachycardia with aberration: value of the clinical history. Ann Emerg Med. 1987;16 (1):40-43. 

Brugada P, Brugada J, Mont L, Smeets J, Andries EW. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation. 1991;83(5):1649-1659. 

Lau EW, Ng GA. Comparison of the performance of three diagnostic algorithms for regular broad complex tachycardia in practical application. Pacing and clinical electrophysiology: PACE. 2002;25(5): 822-827. 

Marx, John A, Robert S. Hockberger, Ron M. Walls, James Adams, and Peter Rosen. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, PA: Mosby/Elsevier; 2010. 

Mathew PK. Diving reflex. Another method of treating paroxysmal supraventricular tachycardia. Arch Intern. Med. 1981;141(1):22-23. 

Stewart RB, Bardy GH, Greene HL. Wide complex tachycardia: misdiagnosis and outcome after emergent therapy. Ann Intern Med. 1986;104 (6):766-771. 

Tintinalli, Judith E, and J S. Stapczynski. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. New York, NY: McGraw-Hill; 2011. 

Wellens HJ, Bar FW, Lie KI. The value of the electrocardiogram in the differential diagnosis of a tachycardia with a widened QRS complex. Am J Med. 1978;64(1):27-33.

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