What are the implications and treatment options for a patient with tachycardia, presenting with a pulse of 135 beats per minute (bpm)?

Management of Tachycardia with Pulse of 135 bpm

The priority is to identify and treat the underlying cause rather than the heart rate itself, as a pulse of 135 bpm is most likely a compensatory physiologic response to an underlying condition rather than the primary problem. 1, 2, 3

Immediate Assessment of Hemodynamic Stability

First, determine if the patient is hemodynamically unstable by assessing for acute altered mental status, ischemic chest pain, acute heart failure, hypotension, or other signs of shock. 1

• If the patient demonstrates rate-related cardiovascular compromise with these signs and symptoms, proceed to immediate synchronized cardioversion. 1
• However, with ventricular rates <150 bpm in the absence of ventricular dysfunction, it is more likely that the tachycardia is secondary to the underlying condition rather than the cause of the instability. 1, 2
• At 135 bpm, the tachycardia itself is unlikely to be causing hemodynamic instability unless there is pre-existing impaired ventricular function. 1, 2

Evaluate for Hypoxemia and Respiratory Distress

Check oxygen saturation immediately and assess for signs of increased work of breathing (tachypnea, intercostal retractions, suprasternal retractions, paradoxical abdominal breathing), as hypoxemia is a common reversible cause of tachycardia. 1

• Provide supplementary oxygen if oxygenation is inadequate or if the patient shows signs of increased work of breathing. 1

Obtain 12-Lead ECG and Establish Monitoring

Obtain a 12-lead ECG immediately to document the rhythm, measure QRS duration, identify P-wave morphology and relationship to QRS complexes, and look for pre-excitation (delta waves suggesting Wolff-Parkinson-White syndrome). 1, 2, 3

• Attach continuous cardiac monitoring, evaluate blood pressure, and establish IV access. 1
• The ECG should not delay immediate cardioversion if the patient is unstable, but is essential for stable patients. 1

Identify the Underlying Cause

Do not treat the heart rate directly with rate-controlling medications; therapy must be directed toward identification and treatment of the underlying cause. 2, 3

Common Physiologic Causes to Evaluate:

• Fever and infection: Check temperature and look for infectious sources. 2, 3
• Hypovolemia/dehydration: Assess volume status, mucous membranes, skin turgor, and urine output. 2, 3
• Anemia: Check hemoglobin/hematocrit if clinically indicated. 2, 3
• Pain: Assess for uncontrolled pain requiring analgesia. 2, 3
• Hyperthyroidism: Obtain TSH testing to exclude thyroid dysfunction, as this commonly presents with persistent tachycardia. 2, 3
• Hypoxia: Already addressed above with oxygen saturation monitoring. 1
• Electrolyte disturbances: Check potassium and magnesium levels, as hypokalemia and hypomagnesemia can precipitate arrhythmias. 1, 4

Critical Pitfall: Sinus Tachycardia vs. Primary Arrhythmia

Sinus tachycardia is the most common tachycardia in critically ill or acutely ill patients and requires no specific antiarrhythmic treatment. 1, 3, 4

• Sinus tachycardia is defined as heart rate >100 bpm originating from the sinus node, and is usually a physiologic response to an underlying stimulus. 1
• When cardiac function is poor, cardiac output can be dependent on a rapid heart rate; in such compensatory tachycardias, "normalizing" the heart rate can be detrimental. 1
• The upper rate of sinus tachycardia is age-related (approximately 220 bpm minus the patient's age in years). 1

Determine if This is a Primary Arrhythmia Requiring Specific Treatment

If the 12-lead ECG reveals a primary arrhythmia rather than sinus tachycardia, specific management is required:

Supraventricular Tachycardia (SVT):

• Atrial fibrillation: Commonly complicates acute illness and myocardial infarction (15-20% of cases), frequently associated with severe left ventricular damage and heart failure. 1

  • In many cases, the ventricular rate is not fast, the arrhythmia is well tolerated, and no treatment is required. 1
  • If the fast rate contributes to heart failure, beta-blockers and digoxin are effective in slowing the rate; amiodarone may be more efficacious in terminating the arrhythmia. 1

• Other SVTs (PSVT, atrial flutter): Usually self-limited and may respond to vagal maneuvers (Valsalva maneuver, carotid massage). 1, 5

  • Adenosine is the first-choice drug for acute SVT if vagal maneuvers fail. 1, 5
  • If the patient has adverse signs or is unresponsive to adenosine, consider beta-blockers, verapamil, or amiodarone. 1

Ventricular Tachycardia:

• Differentiate true ventricular tachycardia from accelerated idioventricular rhythm (a harmless consequence of reperfusion with ventricular rate <120 bpm). 1
• Runs of non-sustained ventricular tachycardia may be well tolerated and do not necessarily require treatment. 1
• Beta-blockers are the first line of therapy unless contraindicated. 1

Immediate Cardiology Referral Criteria

Immediate cardiology referral is required for: 2, 3

• Pre-excitation (Wolff-Parkinson-White syndrome) on ECG 2, 3, 6
• Wide-complex tachycardia of unknown origin 2, 3
• Syncope during tachycardia or with exercise 2, 3
• Documented sustained supraventricular tachycardia 2, 3

Outpatient Monitoring Strategy (If Stable and Discharged)

If palpitations are infrequent and not accompanied by angina, heart failure, or syncope, use event or wearable loop recorders rather than 24-hour Holter monitoring. 2

• For frequent episodes (several per week), 24-hour Holter monitoring may be appropriate. 2
• For less frequent episodes, event or wearable loop recorder is preferred. 2
• For rare symptoms (fewer than two episodes per month), consider implantable loop recorder if symptoms are severe. 2

Additional Investigations

Obtain echocardiography to exclude structural heart disease, which cannot be reliably detected by physical examination or 12-lead ECG alone. 2

• This is particularly important if there is concern for tachycardia-induced cardiomyopathy, which can develop from persistent or highly frequent tachyarrhythmias with uncontrolled heart rate. 7