“…For applied research, it would be pertinent to determine, the lowest MS rates that allow sustenance of 1:1 capture, for instance during AV block, and to compare MS at multiple sites in the same heart, to assess ‘regionality’ of mechanical effects and to explore whether alternating MS between multiple sites could be an effective means of sustaining long-term mechanical pacing. This would also allow one to determine if, in contrast to the present results, previously-reported sustenance of MS in patients 5–8 , 11 is related to differences in pacing rate (below vs. above sinus rate), experimental preparation ( in situ vs. ex situ ), species (human vs. rabbit), MS delivery (extracorporeal vs. epicardial), MS characteristics (such as magnitude and/or rate), and/or other factors. Figure 7Inter-dependence of mechanically-induced excitation on indentation magnitude and rate.…”
Section: Discussioncontrasting
confidence: 51%
“…If applied rhythmically to the precordium (‘precordial percussion’), 5 repetitive thumps have been shown to be an effective means for extracorporeal pacing of the asystolic 6 , 7 or bradycardic 8 heart, while benefits of MS for cardioversion of tachycardias is limited 9 . As mechanically-induced heartbeats have a greater hemodynamic effect than external chest compressions, 10 they can maintain consciousness in patients during extended periods of ventricular standstill (cases as long as 2 h 45 min have been reported) 6 , 11 …”
AimsMechanical stimulation (MS) represents a readily available, non-invasive means of pacing the asystolic or bradycardic heart in patients, but benefits of MS at higher heart rates are unclear. Our aim was to assess the maximum rate and sustainability of excitation by MS vs. electrical stimulation (ES) in the isolated heart under normal physiological conditions.Methods and resultsTrains of local MS or ES at rates exceeding intrinsic sinus rhythm (overdrive pacing; lowest pacing rates 2.5±0.5 Hz) were applied to the same mid-left ventricular free-wall site on the epicardium of Langendorff-perfused rabbit hearts. Stimulation rates were progressively increased, with a recovery period of normal sinus rhythm between each stimulation period. Trains of MS caused repeated focal ventricular excitation from the site of stimulation. The maximum rate at which MS achieved 1:1 capture was lower than during ES (4.2±0.2 vs. 5.9±0.2 Hz, respectively). At all overdrive pacing rates for which repetitive MS was possible, 1:1 capture was reversibly lost after a finite number of cycles, even though same-site capture by ES remained possible. The number of MS cycles until loss of capture decreased with rising stimulation rate. If interspersed with ES, the number of MS to failure of capture was lower than for MS only.ConclusionIn this study, we demonstrate that the maximum pacing rate at which MS can be sustained is lower than that for same-site ES in isolated heart, and that, in contrast to ES, the sustainability of successful 1:1 capture by MS is limited. The mechanism(s) of differences in MS vs. ES pacing ability, potentially important for emergency heart rhythm management, are currently unknown, thus warranting further investigation.
“…For applied research, it would be pertinent to determine, the lowest MS rates that allow sustenance of 1:1 capture, for instance during AV block, and to compare MS at multiple sites in the same heart, to assess ‘regionality’ of mechanical effects and to explore whether alternating MS between multiple sites could be an effective means of sustaining long-term mechanical pacing. This would also allow one to determine if, in contrast to the present results, previously-reported sustenance of MS in patients 5–8 , 11 is related to differences in pacing rate (below vs. above sinus rate), experimental preparation ( in situ vs. ex situ ), species (human vs. rabbit), MS delivery (extracorporeal vs. epicardial), MS characteristics (such as magnitude and/or rate), and/or other factors. Figure 7Inter-dependence of mechanically-induced excitation on indentation magnitude and rate.…”
Section: Discussioncontrasting
confidence: 51%
“…If applied rhythmically to the precordium (‘precordial percussion’), 5 repetitive thumps have been shown to be an effective means for extracorporeal pacing of the asystolic 6 , 7 or bradycardic 8 heart, while benefits of MS for cardioversion of tachycardias is limited 9 . As mechanically-induced heartbeats have a greater hemodynamic effect than external chest compressions, 10 they can maintain consciousness in patients during extended periods of ventricular standstill (cases as long as 2 h 45 min have been reported) 6 , 11 …”
AimsMechanical stimulation (MS) represents a readily available, non-invasive means of pacing the asystolic or bradycardic heart in patients, but benefits of MS at higher heart rates are unclear. Our aim was to assess the maximum rate and sustainability of excitation by MS vs. electrical stimulation (ES) in the isolated heart under normal physiological conditions.Methods and resultsTrains of local MS or ES at rates exceeding intrinsic sinus rhythm (overdrive pacing; lowest pacing rates 2.5±0.5 Hz) were applied to the same mid-left ventricular free-wall site on the epicardium of Langendorff-perfused rabbit hearts. Stimulation rates were progressively increased, with a recovery period of normal sinus rhythm between each stimulation period. Trains of MS caused repeated focal ventricular excitation from the site of stimulation. The maximum rate at which MS achieved 1:1 capture was lower than during ES (4.2±0.2 vs. 5.9±0.2 Hz, respectively). At all overdrive pacing rates for which repetitive MS was possible, 1:1 capture was reversibly lost after a finite number of cycles, even though same-site capture by ES remained possible. The number of MS cycles until loss of capture decreased with rising stimulation rate. If interspersed with ES, the number of MS to failure of capture was lower than for MS only.ConclusionIn this study, we demonstrate that the maximum pacing rate at which MS can be sustained is lower than that for same-site ES in isolated heart, and that, in contrast to ES, the sustainability of successful 1:1 capture by MS is limited. The mechanism(s) of differences in MS vs. ES pacing ability, potentially important for emergency heart rhythm management, are currently unknown, thus warranting further investigation.
“…The fact that a blow to an area of the ventricle treated with aconitine, sodium oxalate, sodium citrate, or hypertonic solutions of sodium chloride may provoke or accelerate a ventricular tachy cardia is established (3). Even in the experiments discussed in this paper mechanical stimulation of the aconitine treated area at a time when sinus rhythm was still present led to the earlier ap pearance of the tachycardia.…”
“…In patients in whom pacing is to be performed but a delay occurs before it can be achieved, external cardiac percussion (known as "fist" or "thump" pacing) may generate QRS complexes with an effective cardiac output, particularly when myocardial contractility is not critically compromised. [106][107][108] External cardiac percussion is performed with blows at a rate of 100/minute, given with less force than a precordial thump and delivered over the heart, not the sternum. Conventional cardiopulmonary resuscitation should be substituted immediately if QRS complexes with a discernible output are not being achieved.…”
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