The AHA Guidelines and Scientific Statements Handbook

The AHA Guidelines and Scientifi c Statements Handbook

Wide QRS-complex tachycardia

(QRS duration greater than 120 ms)

Regular or irregular?

Irregular

Atrial fibrillation

Atrial flutter/AT with variable

conduction and

a) BBB or

b) antegrade conduction via AP

Regular

Vagal maneuvers

or adenosine

Is QRS identical to that during SR?

If yes, consider:

• SVT and BBB


• Antidromic AVRT†
  Previous myocardial infarction or
  structural heart disease? If yes,
  1 to 1 AV relationship? VT is likely.

V rate faster than A rate A rate faster than V rate

Atrial tachycardia

Atrial flutter

VT

Yes or No

unknown

QRS morphology in precordial leads

Typical RBBB

or LBBB SVT

Precordial leads

• Concordant*


• No R/S pattern


• Onset of R to nadir
  longer than 100 ms

VT

RBBB pattern

• qR, Rs or Rr^1 in V 1


• Frontal plane axis
  range from +90 degrees
  to –90 degrees

VT

LBBB pattern

• R in V 1 longer than 30 ms


• R to nadir of S in V 1
  greater than 60 ms


• qR or qS in V 6

VT

Fig. 16.3 Differential diagnosis for wide QRS-complex tachycardia (more than 120 ms). A QRS morphology analysis is of less value in the
presence of QRS conduction delay during sinus rhythm. *Concordant indicates that all precordial leads show either positive or negative
defl ections. †In preexcited tachycardias, the QRS is generally wider (i.e., more preexcited) compared with sinus rhythm. A indicates atrial; AP,
accessory pathway; AT, atrial tachycardia; AV, atrioventricular; AVRT, atrioventricular reciprocating tachycardia; BBB, bundle-branch block;
LBBB, left bundle-branch block; ms, milliseconds; QRS, ventricular activation on ECG; RBBB, right bundle-branch block; SR, sinus rhythm;
SVT, supraventricular tachycardias; V, ventricular; VF, ventricular fi brillation; VT, ventricular tachycardia.

can be helpful in differentiating VT from SVT
(Fig. 16.3).
Indications for referral to an arrhythmia specialist
include:

• Patients with Wolf–Parkinson–White syndrome
  (presence of pre-excitation and arrhythmia).


• Patients with severe symptoms (syncope or
  dyspnea) during palpitations.


• Wide QRS-complex tachycardia of unknown origin.


• Narrow QRS-complex tachycardia with drug-
  resistance or intolerance, or patients desire to be free
  from drug therapy.

Management

If the diagnosis of SVT can not be proven, the patient

should be treated as if VT was present. Medications

for SVT (Verapamil or diltiazem) may precipitate

hemodynamic collapse for a patient with VT. Ade-

nosine should be used with caution when the diag-

nosis is unclear, because it may produce VF in

patients with coronary artery disease. Adenosine

may also precipitate AF with a rapid ventricular rate

in patients with preexcitation. Immediate DC car-

dioversion is the treatment for hemodynamically

unstable tachycardias. Recommendations for acute