When I was in school, I was taught that the precordial thump(PT) is only used in witnessed ventricular fibrillation or ventricular tachycardia arrest. It was a first line treatment and most-likely feeble attempt to convert the patient into a perfusable rhythm. It was taught as harmless.

I recently read an article from JEMS online: To Thump or Not To Thump(1)
Here are some things that stood out:

In the unwitnessed arrests, only two patients had changes in their rhythm associated with PT. One was in PEA that converted to asystole, and no return of spontaneous circulation(ROSC) was achieved. The second was in V Tach and converted to PEA without ROSC.

PT was performed three times in witnessed arrests, and all three had ROSC. In all three cases the patients developed asystole, and PT resulted in the spontaneous return of a pulse. They subsequently received pacemakers.

Amazing. First of all, every witnessed arrest was asystole. I wonder if these patients were bradycardic or severely hypoxic. Secondly, PT works for asystole?

[t]he fact that the cases where PT worked were on patients in asystole is astounding. Not only is this a remarkable finding, but one that would have otherwise generated several case reports. Most providers have been taught that PT is only for V Fib/V Tach and that a patient who goes into asystole gets CPR, pharmacology and pacing

My thoughts exactly. Actually we don't pace asystole anymore, but this article made me research why. I mean if a PT will convert patients why not defibrillation or pacing?

From the New England Journal of Medicine(2):

Background: Transcutaneous cardiac pacemakers generate electrical stimuli that pace the heart through external electrodes that adhere to the chest wall. Transcutaneous pacing has been useful in some patients with bradycardia, but its efficacy in patients with asystole and full cardiac arrest has been limited, possibly because of delays in the initiation of pacing. We studied the efficacy of early transcutaneous pacing in patients with out-of-hospital asystolic cardiac arrest.Conclusions: Transcutaneous pacing appears to offer no benefit in patients with asystolic cardiac arrest, even when it is performed as early as possible by EMTs in the field. Our data suggest that the widespread implementation of early transcutaneous pacing for out-of-hospital asystolic cardiac arrest would be ineffective.

So pacing won't work, how about defibrilation?
From The American Journal of Emergency Medicne(3):

Standard drug therapy for asystole during cardiac arrest includes epinephrine, atropine, and calcium chloride (CaCl). Recent studies have shown that ventricular fibrillation (VF) can appear to be asystole when recorded from the chest surface. To determine the efficacy of these drugs and electrical countershock for asystole, a group of 83 adult nontraumatic cardiac arrest victims (55 men, 28 women, mean age of 64 +/- 14 years) were studied. Asystole appeared at some time during arrest in 44 patients (53%) and was the initial rhythm in 24 (29%). The rate of survival to hospital discharge was significantly higher in patients whose initial rhythm was VF (46%) than in patients whose initial rhythm was asystole (0%). Epinephrine, CaCl and atropine infrequently changed the rhythm from asystole. Electrical countershock infrequently altered the rhythm from asystole when it appeared as the initial rhythm. However, countershock was significantly more effective than epinephrine (P less than 0.003), atropine (P less than 0.04), or CaCl (P less than 0.03) in altering the rhythm from asystole, which appeared later in resuscitation. Ventricular fibrillation was the most common rhythm appearing after countershock for asystole. Countershock appears to be superior to epinephrine, CaCl, and atropine for treating asystole during the course of resuscitation, suggesting that the rhythm diagnosed as asystole may actually be VF in many cases.

Okay, I actually think that this just proves that some of us aren't very good at identifying asystole. Remember that more than one lead rule? I don't think this study proves that shocking asystole works, but what if the patients in the PT study from JEMS were actually in v-fib? If this study is right, they may have misinterpreted the rhythym and successfully converted v-fib with a PT.

Does PT work?
Back in '84 the Anals..cough..Annals of Emergency Medicine(4) thought so:

Precordial thump is considered a useful manoeuver in cardiac arrest and ventricular tachycardia. On ecg recordings we have observed that the precordial thump has always been followed by an atrial or ventricular depolarization (premature beats), which is responsible for the cardiac electric activity enhancement and for the interruption of reentrant mechanism in ventricular and supraventricular tachycardias.

Resuscitation(5) says otherwise:

INTRODUCTION: Reports about the efficacy of precordial thump (PT)in the termination of ventricular arrhythmias (VA) vary widely.
[...]
CONCLUSION: Efficacy of PT in termination of induced non-tolerated VA is very low even with early application after VA onset.

So what are the risks of a PT?

More from the JEMS article:

PT had neither positive nor detrimental effects in non-EMS-witnessed cardiac arrests, and it was ineffective in tachyarrhythmic cardiac arrest and pulseless electrical activity

But is it harmless?

In the prehospital setting the precordial thump is usually not beneficial, and may be detrimental. Thus its use as the initial maneuver in treating the cardiac arrest patient with VT or VF in this setting cannot be supported. The presence of acidosis and hypoxia may explain why prehospital precordial thump responses differ from those seen in the hospital environment.

It might be detrimental? I also read a study with a case of a sternal fracture following the PT. So what's left?

From the Canadian Journal of Emergency Medical Care(6):

[...]CONCLUSIONS: In a BLS-D system, there is a very low but measurable survival rate for prehospital asystolic cardiac arrest. CRIs of over 8 minutes were associated with 100% nonsurvival, whereas unwitnessed arrests with no bystander CPR were not. These data add to the growing literature that will help guide ethical decision-making for protocol development in emergency medical services systems.

If the medical literarure is going to actually change our protocols, someone has gotta read this one (7):

OBJECTIVES: To study the factors associated with short- and long-term survival after asystolic out-of-hospital cardiac arrest, with a reference to medical futility. METHODS: This is a retrospective observational study conducted in Helsinki, Finland during 1 January 1997 to 31 December 2005. All out-of-hospital cardiac arrests were prospectively registered in the cardiac arrest database. Of 3291 arrests, 1455 had asystole as the first registered rhythm. These patients represent the study population. RESULTS: A short time interval to the initiation of advanced life support (ALS) was associated with a long-term benefit, but a short first responding unit (FRU) response time had only a short-term benefit. Conversion of asystole into a shockable rhythm provided only a short-term benefit. The prognosis was poor if the FRU response time was over 10 min or the ALS response time was over 11 min in bystander-witnessed arrests, and if the duration of resuscitation was over 8 min in emergency medical services (EMS)-witnessed arrests. Bystander-CPR was associated with increased 30-day mortality. The 30-day survival rate after an unwitnessed arrest (n=548) was 0.5%. All survivors in this group were either hypothermic or were victims of near-drowning. CONCLUSIONS: Resuscitation should be withheld in cases of unwitnessed asystole, excluding cases of hypothermia and near-drowning. The prognosis is poor if the FRU response time is over 10 min or the ALS response time is over 10-15 min in bystander-witnessed arrests. The decision of whether or not to attempt resuscitation should not be influenced by the presence of bystander-CPR. Early initiation of ALS should be prioritised in the treatment of out-of-hospital asystole.

Okay, so in conclusion, the results are inconclusive. There has to be more than one study that says the PT will convert a withnessed asystolic arrest for anyone to adopt it as a new treatment. The risks are pretty small, but they exist. We may want to relook AHA's recomondation of the use of the PT on a witnessed VF/VT arrest. The results of multiple studies may indicate that the cardiac ischemia, the patient's in the prehospital enviroment will present with, will probably inhibit the conversion from PT. We have all seen a doc do it though, right?

Just thought I would share my research with you, enjoy!

References:

(1)Wesley K. 2009. "To Thump or Not To Thump The value of the precordial thump"Journal of Emergency Medical Services, Street Science.
(2)Cummins RO, Graves JR, Larsen MP, Hallstrom AP, Hearne TR, Ciliberti J, Nicola RM, and Horan S. 1993. "Out-of-hospital transcutaneous pacing by emergency medical technicians in patients with asystolic cardiac arrest." The New England Journal Of Medicine 328, no. 19: 1377 1382. MEDLINE with Full Text, EBSCOhost (accessed May 15, 2009).
(3)Ornato JP, Gonzales ER, Morkunas AR, Coyne MR, and Beck CL. 1985. "Treatment of presumed asystole during pre-hospital cardiac arrest: superiority of electrical countershock." The American Journal Of Emergency Medicine 3, no. 5: 395-399. MEDLINE with Full Text, EBSCOhost (accessed May 15, 2009).
(4)Miller J, Tresch D, Horwitz L, Thompson BM, Aprahamian C, and Darin JC. 1984. "The precordial thump." Annals Of Emergency Medicine 13, no. 9 Pt 2: 791-794. MEDLINE with Full Text, EBSCOhost (accessed May 15, 2009).
(5)Haman L, Parizek P, and Vojacek J. 2009. "Precordial thump efficacy in termination of induced ventricular arrhythmias." Resuscitation 80, no. 1: 14-16. MEDLINE with Full Text, EBSCOhost (accessed May 15, 2009).
(6)Petrie DA, De Maio V, Stiell IG, Dreyer J, Martin M, and O'brien JA. 2001. "Factors affecting survival after prehospital asystolic cardiac arrest in a Basic Life Support-Defibrillation system." CJEM: Canadian Journal Of Emergency Medical Care = JCMU: Journal Canadien De Soins Médicaux D'urgence 3, no. 3: 186-192. MEDLINE with Full Text, EBSCOhost (accessed May 15, 2009).
(7)Väyrynen T, Kuisma M, Määttä T, and Boyd J. 2008. "Medical futility in asystolic out-of hospital cardiac arrest." Acta Anaesthesiologica Scandinavica 52, no. 1: 81-87. MEDLINE with Full Text, EBSCOhost (accessed May 15, 2009).