Failure to capture pacemaker4/9/2023 ![]() Careful review of an ECG or even a good-quality rhythm strip used during echocardiography can diagnose this condition and promote expedient treatment.In patients with pacemakers, hyperkalaemia causes three important abnormalities that usually become manifest when the K level exceeds 7 mEq/L: (i) widening of the paced QRS complex from delayed intraventricular conduction velocity, (ii) Increased atrial and ventricular pacing thresholds that may cause failure to capture. Pacemaker syndrome is often underdiagnosed despite being so readily treatable. ![]() Gross abnormalities on ECGs that raise the possibility of pacemaker syndrome are retrograde conduction, prolonged PR intervals (greater than 300 ms), loss of atrial capture and nodal rhythms, which are faster than the atrial rate. ![]() International guidelines advocate dual chamber pacing as a first choice in patients with intermittent and persistent sinus node disease ( 3). In a randomised crossover clinical trial, 75% of patients who said they were satisfied with ventricular demand pacing (VVI) experience symptomatic and functional improvement when changed to dual chamber mode (DDD) ( 2). The true incidence is likely to be higher. A fifth of patients with sinus node disease implanted with a single chamber pacemaker with a right ventricular lead go on to develop pacemaker syndrome ( 1). As it is pertinent to our presented case, we will focus on the latter cause.Ī definition of pacemaker syndrome is not universally accepted but is considered when heart failure symptoms are associated with AV dysynchrony. All of these can be identified during a standard transthoracic echocardiogram. Iatrogenic causes of new-onset or progressive heart failure symptoms in patients implanted with cardiac rhythm management devices include: (1) pacing-induced left ventricular systolic dysfunction (this is most commonly observed in patients who predominately have a high burden of right ventricular pacing but may also be seen in patients with biventricular devices, particularly if the left ventricular lead is inappropriately pacing the apex of the heart) (2) pacemaker wire-related interference with tricuspid or rarely pulmonary valve function and (3) pacemaker syndrome. This case report emphasises the value of an adequate quality ECG trace when performing an echocardiogram and the significance of using all modalities available during a study to assess AV synchrony. A repeat pacing check showed the right atrial pacing burden to be 54% and right ventricular pacing burden <1%. The trans-mitral pulse wave Doppler trace confirmed AV synchrony following the atrial lead upgrade ( Fig. Her repeat echocardiogram showed that the right ventricle had remodelled and the tricuspid valve leaflets were now co-apting ( Fig. The patient underwent an upgrade to a dual chamber system with an addition of an atrial lead. This could have been identified at the pacemaker check also. Retrograde A waves are consistently seen following each right ventricle paced complex, resulting in a pacemaker syndrome. 3), it was apparent that this patient had cardioverted into sinus rhythm and had developed atrioventricular (AV) dyssynchrony. 3) and the rhythm strip of the transthoracic echocardiogram ( Fig. On closer inspection of the previous 12 lead ECG ( Fig. The treating team began discussing palliative options but requested our second opinion. The patient was discharged home and in the subsequent two months had two further admissions with decompensated heart failure. She remained on warfarin (indication: stroke thromboprophylaxis) with international normalised ratios in the therapeutic range and hence pulmonary embolism was not considered likely. The patient was treated as heart failure with preserved ejection fraction with intravenous diuretics.
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