Adenosine versus intravenous calcium channel antagonists for supraventricular tachycardia

Paolo Balzaretti

S.C. Medicina e Chirurgia d’Accettazione e Urgenza,A.O. “Ordine Mauriziano”, Torino

What we already know about this topic

Paroxysmal supraventricular tachycardia (PSVT) is a rather common arrhythmia in the Emergency Department, with an incidence of 35 cases per 100,000 person-years (1). Patients usually complain sudden onset of palpitations, anxiety, light-headedness and neck-pounding. 12-lead electrocardiogram shows a regular tachycardia with narrow QRS-complexes and heart rate > 110 bpm.
Even if often presented as the first choice for arrhythmia termination, vagal maneuvers are poorly effective, with a success rate of about 20% (2). If PSVT does not respond to vagal maneuvers, ACLS Guidelines recommend giving 6 mg of adenosine as a rapid IV push (3). Similar indications can be found in the “2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia” (4).
Nonetheless, non-dihydropyridine calcium channel blockers (CCB) (verapamil and diltiazem), even if considered second line agents by these documents, showed high efficacy in the past (5), constituting a reasonable alternative to adenosine. To further clarify the clinical efficacy of these drugs in respect to the latter, Alabed et al. conducted a systematic review (6).

The Cochrane review (6)

Title: Adenosine versus intravenous calcium channel antagonists for supraventricular tachycardia.

Authors: Alabed S, Sabouni A, Providencia R, Atallah E, Qintar M, Chico TJA.

Bibliographic citation: Cochrane Database Syst Rev 2017; 10: CD005154.

Objective: to review all randomized controlled trials (RCTs) that compare effects of adenosine versus CCB in terminating PSVT.

Included studies: randomized controlled comparing intravenous calcium channel blocker and adenosine.

Primary outcome:

reversion to sinus rhythm,
major adverse events (defined as cardiac arrest, prolonged hypotension, symptomatic bradycardia requiring treatment, and acute cardiac failure).

Secondary outcomes:

time to reversion to sinus rhythm,
rate of relapse to PSVT within two hours after reversion, length of stay in hospital, minor adverse events, patient satisfaction as measured on any validated scale.

Number of included studies: seven.

Quality of included studies: overall quality of included study is low (particularly regarding blinding of participants and personnel and blinding for outcome assessment). No clear information are available for other possible causes of bias for majority of studies.

Number of patients: 622.

Results:

Table 1.Results of the systematic review. Conclusions may be drawn only for main outcome.

Comment and conclusions

Results from this systematic review demonstrate similar clinical efficacy of adenosine and CCB (89.7% and 92.9% respectively). Data about adverse events are low quality; minor adverse events like chest tightness and flushing appeared more frequent in patients treated with adenosine.

Biases regarding blinding of participants and personnel and about blinding for outcome assessment implied a downgrading of quality of evidence to moderate. Other limitations are the moderate heterogeneity (I2 = 36%), mainly related to varying doses of the drugs used and the small size of the included studies (less than 100 patients, except for the trials of Lim et al. and Cheng et al).

Moderate quality evidence shows that efficacy of CCB is similar to that of adenosine in adult patients with PSVT in the Emergency Department. Verapamil was the drug more frequently employed (5 mg bolus, repeated two or three times). In daily practice, patients often complain bothering symptoms after adenosine administration, like chest tightness and a feeling of impending death: further studies are required to clarify patient preferences and satisfaction, important aspects to deal with when choosing a therapeutic strategy.

Note: dosage of the cited drugs and contraindications (3,4)

Adenosine: 6 mg of IV as a rapid IV push through a large (eg, antecubital) vein followed by a 20 mL saline flush. If the rhythm does not convert within 1 to 2 minutes, give a 12 mg rapid IV push using the method above.
Verapamil, give a 2.5 mg to 5 mg IV bolus over 2 minutes (over 3 minutes in older patients). If there is no therapeutic response and no drug-induced adverse event, repeated doses of 5 mg to 10 mg may be administered every 15 to 30 minutes to a total dose of 20 mg.
Diltiazem, give a dose of 15 mg to 20 mg (0.25 mg/kg) IV over 2 minutes; if needed, in 15 minutes give an additional IV dose of 20 mg to 25 mg (0.35 mg/kg). The maintenance infusion dose is 5 mg/hour to 15 mg/hour, titrated to heart rate.

CCB should be given only to patients with narrow-complex reentry SVT or arrhythmias known with certainty to be of supraventricular origin. Verapamil should not be given to patients with wide-complex tachycardias or in case ventricular tachycardia or pre-excited AF are a matter of concern, because these patients may become hemodynamically unstable and develop ventricular fibrillation after verapamil or diltiazem administration. CCB should not be given to patients with impaired ventricular function, heart failure or hemodynamical instability.

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