Although there is a crescendo-decrescendo pattern, this is NOT enough to satisfy the diagnosis of TDP.
This crescendo-decrescendo pattern in V-fib is common in the first few minutes after arresting.
Notice that there is a definite point of the QRS and a rounded T side with TDP. Note that the points keep twisting up then down. Also observe the rate differences. Vf has rates of 300-500 impulses per minute where as TDP tends to be slower.
What is the difference? The name Torsade de Pointes is a French term that literally means torsion or twisting of the points. These patients usually have a cause for TDP such as hypomagnesemia, cardiomyopathy, antiarrhythmic drugs like Amiodarone or Quinidine, or mixing drugs such as oral antifungals with Seldane or Propulsid. Another difference is that occasionally, patients in TDP can remain conscious, although usually very symptomatic. Another feature is that TDP can "break" spontaneously and come and go.
Ventricular fibrillation will always cause a loss of consciousness within 20 seconds of its onset. It is very unlikely that V-fib will self correct.
What is the big deal? Treatment options will differ between the two. Manage Vf as you usually do. This would include immediate defibrillation and antiarrhythmic therapy such as IV Lidocaine 1 to 1.5 mg / kg of body weight and a maintainance drip. With TDP once you have converted the patient back into a stable rhythm, efforts should be made to keep the QT interval as short as possible. This may mean heart rate elevation, and withholding antiarrhythmics. If your patient has risk factors for hypomagnesemia, such as diabetes, diuretic therapy, anorexia, alcoholism, gastointestinal malabsorbsion, or ileo-jejunal bypass, then 1 - 2 gms of magnesium sulfate should be given slowly IV. MgSO4 has been show to be effective even if the patient is not magnesium deficient. Call your medical control physician for guidance.
Updated: November 8, 1999