Tag Archives: EKG

The “3 SIMPLE Rules”: an easy and accurate tool for recognizing VT

17 Dec
Following the discussion on ectopy and aberrancy (view Ectopy or aberrancy? Google Ecg+ community comments on a clinical case.)  Ken Grauer, EKG master and author of many EKG books, gave us the permission to share his “3 SIMPLE Rules” to recognize VT in a simple ad accurate way.
 

  • Rule #1 Is there extreme axis deviation during WCT

Extreme axis deviation is easy to recognize. The QRS complex will be entirely negative in either lead I or lead aVF. The presence of extreme axis deviation during a WCT rhythm is virtually diagnostic of VT.

  • Rule #2 Is lead V6 all (or almost all) negative?

IF ever the QRS in lead V6 is either all negative (or almost all negative)  then VT is highly likely.

  • Rule #3 Is the QRS during WCT “ugly”?

The “uglier” the QRS the more likely the rhythm is. VT originates from a ventricular focus outside of the conduction system. As a result VT is more likely to be wider and far less organized (therefore “uglier”) in its conduction pattern
 
The “3 simple rules” is an extract from ACLS 2013 Arrhythmias  where you can find the complete explanation and much more on arrhythmias.
Visit Ken Grauer Amazon page to find out more and discover all the amzing EKG books he wrote. They are accurate and reliable for use in many emergency situation.
I’ll include Ken’s reply in the main script of the post cause it contains some very important adjuncts and expalnations. At the end of the replay you’ll find the link to download the full text of the section regarding the WCT topic. You’ll also appreciate the perfect Ken’s italian. I’m amazed….
“Molto grazie Mario per la pubblicazione del mio consiglio su le tre semplici regole per diagnosticare VT! I’ll make a few brief additions to what Mario wrote. RULE #1 – Remember that slight or even moderate axis deviation is of no help. The QRS complex must be ALL negative in either lead I or in lead aVF. If it is – then the rhythm is almost always VT. RULE #2 – Again, moderate negativity in lead V6 is common and means nothing. But if the QRS complex in lead V6 is either all negative or shows no more than a tiny r wave – then VT is likely. This is because such marked negativity in lead V6 implies that the impulse is moving away from the apex – and that almost always means VT. RULE #3 – Supraventricular rhythms with either preexisting bundle branch block or aberrant conduction typically resemble some form of conduction defect (ie, either RBBB, LBBB or RBBB with LAHB and/or LPHB). However, if the QRS complex is amorphous (ie, very “ugly” and formless) – then it is much more likely to be originating from the ventricles. Occasionally, patients may have unusual forms of IVCD – so this rule is not 100% accurate – but it is a helpful supportive point in the differential diagnosis. For those wanting more complete description of the 3 Rules (and other pointers in assessing wide tachycardias) – feel free to download these Sections from my ACLS-2013-ePub – GO TO – https://www.dropbox.com/s/8bc9h5cumo7e4vy/8.0%2C9.0%2C10.0-%20ACLS-2013-e-PUB-WCT-Criteria-%2810-13.11-2014%29-LOCK.pdf?dl=0 – Detailed description of the 3 Simple Rules begins in Section 08.17. Spero che questo vi aiuta.”
Ken Grauer
Logo MEDEST2

Tags: , , , ,

Aberranza od ectopia nelle tachiaritmie a complessi larghi: un metodo “one step” per fare diagnosi.

25 Sep

Vtach question mark

La diagnosi elettrocardiografica delle tachiaritmie a complessi larghi pone spesso il medico d’urgenza di fronte ad un dilemma culturale e clinico.

La localizzazzione del foco ectopico o il riconoscimento dell’aberranza infatti non sono un mero esercizio accademico ma un’informazione determinante per il proseguio del percorso terapeutico.

Molti metodi che utilizzano criteri clinici e morfologici sono stati indicati come adiuvanti nella diagnosi in caso di tachiaritmie a complessi larghi.

I criteri clinici si sono dimostrati nel corso degli anni poco affidabili ed addirittura fuorvianti.

I criteri morfologici hanno specificità e sensibilità tra di loro diverse.

  • Brugada Algorithm: SN 89%, SP 59.2%
  • Vereckei aVR Algorighm: SN 87.1%, SP 48%
  • Bayesian Algorithm: SN 89%, SP 52%
  • Griffith (Bundle Branch Block) Algorithm: SN 94.2%, SP 39.8%

Tra tutti quello che sicuramente ha riscosso più fortuna è il metodo di Brugada.

http://academiclifeinem.com/wp-content/uploads/2013/08/Screen-Shot-2013-08-21-at-5.39.11-PM.png

http://academiclifeinem.com/wp-content/uploads/2013/08/Screen-Shot-2013-08-21-at-5.39.32-PM.png

Attribution: ALIEM Academic Life In Emergency Medicine

Il metodo di Brugada è sicuramente poco maneggevole nel setting dell’emergenza, perchè è multi-step e quindi di difficile memorizzazione ed applicabilità.

Il metodo R-Wave Peak Time (RWPT) è sicuramente un metodo di semplice uso e di facile memorizzazione.

E’ one-step e si applica in derivazione D2 che è la derivazione più comunemente usata quando facciamo diagnosi di ritmo dal monitor-defibrillatore

Consiste nel misurare l’intervallo tra la fine dell’isoelettrica e il primo cambiamento di direzione dell’asse del QRS.

http://academiclifeinem.com/wp-content/uploads/2013/08/619px-RWPT-2.png

Attribution: ECGpedia.org

La diagnosi di Tachcicardia Ventricolare può essere posta quando questo intervallo ≥ 50 ms.

Il criterio dimostra una buona sensitività e specificità, anche se è stato finora validato su un campione limitato di pazienti

 Sensitivity  93.2% 
 Specificity  99.3% 
 Positive Predictive Value  98.2% 
 Negative Predictive Value       93.3% 

Quello che sembra l’uovo di colombo  nelle tachiaritmie a complessi larghi in effetti introduce un criterio interessante, ma pone la difficile condizione di dover calcolare con precisione la fine dell’isoelettrica ed il cambio di direzione dell’asse del QRS, per poterlo applicare correttamente.

Bottom line:

Aberranza o ectopia?

  • I criteri clinici sono inaffidabili e fuorvianti.

  • I criteri morfologici classici e multi-step sono difficilemtne applicabili in emergenza.

  • Il metodo R-Wave Peak Time (RWPT) è affidabile e riproducibile.

  • E’ auspicabile una misurazione elettronica del criterio da esso utilizzato per renderlo applicabile.

  • Sono sicuramente necessari studi che lo validino su un campione più ampio di pazienti.

References:

  1. P. Brugada, J. Brugada, L. Mont, J. Smeets, and E.W. Andries, “A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex.”, Circulation, 1991.
  2. A. Vereckei, G. Duray, G. Szénási, G.T. Altemose, and J.M. Miller, “Application of a new algorithm in the differential diagnosis of wide QRS complex tachycardia.”, European heart journal, 2007.
  3. E.W. Lau, R.K. Pathamanathan, G.A. Ng, J. Cooper, J.D. Skehan, and M.J. Griffith, “The Bayesian approach improves the electrocardiographic diagnosis of broad complex tachycardia.”, Pacing and clinical electrophysiology : PACE, 2000.
  4. M.J. Griffith, C.J. Garratt, P. Mounsey, and A.J. Camm, “Ventricular tachycardia as default diagnosis in broad complex tachycardia.”, Lancet, 1994.
  5. L.F. Pava, P. Perafán, M. Badiel, J.J. Arango, L. Mont, C.A. Morillo, and J. Brugada, “R-wave peak time at DII: a new criterion for differentiating between wide complex QRS tachycardias.”, Heart rhythm : the official journal of the Heart Rhythm Society, 2010.
  6. T. Datino, J. Almendral, P. Avila, E. González-Torrecilla, F. Atienza, A. Arenal, and F. Fernández-Avilés, “Specificity of electrocardiographic criteria for the differential diagnosis of wide QRS complex tachycardia in patients with intraventricular conduction defect.”, Heart rhythm : the official journal of the Heart Rhythm Society, 2013.

Tags: , , , , , ,