Design for ambulances.

SIR,-Dr. 1). V&el (4 May, p. 301) raises several interesting points concerning the choice of a system for long-term cardiac pacing, but I do not think it is correct foi comparisons to be made between a nationwide survey of implanted pacemakers and the results obtained at one special centre using the induction method. It is a simple matter to select another centre using implantable pacemakers with results fully comparable tc those obtained by Dr. Verel. The paper by Mr. W. Forbes and others (6 April, p. 13) provides such an example. The advantages in keeping the pulse generator outside the body quoted by Dr. Veel are accompanied by disadvantages he omits to mention. Among these are the risk of displacement of the external coil and the possibility that the patient may turn off his pacenaker either deliberately or by mistake, The controls are available equally to the uninformed patients as to the informed. The prevention of competition between sinus and paced rhythms by cessation of pacing is dangerous, since heart block frequently returns, and deaths have been reported when this policy was followed. The use of implantable demand pacemakers deals very satisfactorily with the problem of patients who return to sinus rhythm, but no demand version of the induction system is available as yet. Dr. Verel has misquoted my survey (6 April, p. 11) as showing that 57% of the implanted pacemakers had failed, whereas the true figure should be 41% (116 failures in 278 implanted pacemakers). Since this includes battery exhaustion it could be claimed that the Lucas pacemaker fails regularly every month, and in some cases every week. These comments are in no way intended as a criticism of the excellent clinical results obtained with induction pacemakers, but to suggest that comparison of the survey for implantable pacemakers can only be made with a similar nation-wide survey of the induction system.-I am, etc.,