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1.
The Cardiac Pacemaker Clinic: Memories From a Bygone Era.
Mond, HG, Sloman, JG
Heart, lung & circulation. 2021;(2):216-224
Abstract
In 1963, soon after the first ventricular pacemakers were implanted at the Royal Melbourne Hospital, attempts were made to identify impending pacing failure, thus preventing sudden death in these very vulnerable patients. By 1970, patient numbers had increased, a formal regular pacemaker clinic was established, and guidelines and protocols developed. The clinic was staffed by a physician, a biomedical engineer and cardiac technicians. The unipolar, asynchronous, non-programmable pulse generators were powered by mercuric oxide/zinc batteries and implanted in the abdomen, using either transvenous or epimyocardial leads. Although, pulse generators were electively replaced at 3 years, most had already been replaced because of power source depletion, electronic failure or lead issues. Testing in all patients involved an electrocardiographic rhythm strip and electronic analysis of the stimulus artefact using a calibrated high-speed storage oscilloscope. Results were compared to previous studies and significant changes were interpreted as impending power source depletion. As a result of this testing, 97% of cases of impending power source depletion were detected prior to failure. These findings allowed testing each 4 months and for pulse generator life to be extended beyond three years. With ventricular triggered pulse generators, new testing procedures were designed. With time, visiting regional centres and clinical evaluation of new products became important functions of the clinic.
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2.
Cardiac automaticity: basic concepts and clinical observations.
Vetulli, HM, Elizari, MV, Naccarelli, GV, Gonzalez, MD
Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing. 2018;(3):263-270
Abstract
PURPOSE The purpose of this report was to review the basic mechanisms underlying cardiac automaticity. Second, we describe our clinical observations related to the anatomical and functional characteristics of sinus automaticity. METHODS We first reviewed the main discoveries regarding the mechanisms responsible for cardiac automaticity. We then analyzed our clinical experience regarding the location of sinus automaticity in two unique populations: those with inappropriate sinus tachycardia and those with a dominant pacemaker located outside the crista terminalis region. RESULTS We studied 26 patients with inappropriate sinus tachycardia (age 34 ± 8 years; 21 females). Non-contact endocardial mapping (Ensite 3000, Endocardial Solutions) was performed in 19 patients and high-density contact mapping (Carto-3, Biosense Webster with PentaRay catheter) in 7 patients. The site of earliest atrial activation shifted after each RF application within and outside the crista terminalis region, indicating a wide distribution of atrial pacemaker sites. We also analyzed 11 patients with dominant pacemakers located outside the crista terminalis (age 27 ± 7 years; five females). In all patients, the rhythm was the dominant pacemaker both at rest and during exercise and located in the right atrial appendage in 6 patients, in the left atrial appendage in 4 patients, and in the mitral annulus in 1 patient. Following ablation, earliest atrial activation shifted to the region of the crista terminalis at a slower rate. CONCLUSIONS Membrane and sub-membrane mechanisms interact to generate cardiac automaticity. The present observations in patients with inappropriate sinus tachycardia and dominant pacemakers are consistent with a wide distribution of pacemaker sites within and outside the boundaries of the crista terminalis.
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3.
A longer total duration of rapid ventricular pacing does not increase the risk of postprocedural myocardial injury in patients who undergo transcatheter aortic valve implantation.
Okitsu, K, Iritakenishi, T, Imada, T, Iwasaki, M, Shibata, SC, Fujino, Y
Heart and vessels. 2017;(9):1117-1122
Abstract
Rapid ventricular pacing (RVP) is used during transcatheter aortic valve implantation (TAVI). RVP disturbs myocardial oxygen balance, and when prolonged, it may cause procedure-related myocardial injury (PMI). This study investigated whether a longer duration of RVP increased the occurrence of PMI or worsened long-term mortality after TAVI. We retrospectively analyzed data from 188 patients who underwent TAVI in our institute from January 2013 to July 2015. Myocardial injury was represented by the peak value of creatine kinase-myocardial band (CK-MB) within 72 h after the procedure; an increase greater than 5 times the upper reference limit was regarded as PMI. There was no difference in RVP time (RVPT) between patients with and without PMI (median [range]: 57 [9-189] s vs. 54 [0-159] s, p = 0.9). A higher peak CK-MB was significantly correlated with the apical approach for the procedure (p < 0.001) but not with total RVPT (p = 0.22). A subanalysis of 133 patients whose troponin I was tested within 72 h postprocedurally showed no correlation between the peak value and RVPT (p = 0.40). Shortening RVPT did not result in myocardial protection; thus, RVPT during TAVI should be sufficient to optimize valve placement.
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4.
Acute Optogenetic Modulation of Cardiac Twitch Dynamics Explored Through Modeling.
Aboelkassem, Y, Campbell, SG
Journal of biomechanical engineering. 2016;(11):1110051-11100511
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Abstract
Optogenetic approaches allow cellular membrane potentials to be perturbed by light. When applied to muscle cells, mechanical events can be controlled through a process that could be termed "optomechanics." Besides functioning as an optical on/off switch, we hypothesized that optomechanical control could include the ability to manipulate the strength and duration of contraction events. To explore this possibility, we constructed an electromechanical model of the human ventricular cardiomyocyte while adding a representation of channelrhodopsin-2 (ChR2), a light-activated channel commonly used in optogenetics. Two hybrid stimulus protocols were developed that combined light-based stimuli with traditional electrical current (all-or-none) excitation. The first protocol involved delivery of a subthreshold optical stimulus followed 50-90 ms later by an electrical stimulus. The result was a graded inhibition of peak cellular twitch force in concert with a prolongation of the intracellular Ca2+ transient. The second protocol was comprised of an electrical stimulus followed by a long light pulse (250-350 ms) that acted to prolong the cardiac action potential (AP). This created a pulse duration-dependent prolongation of the intracellular Ca2+ transient that in turn altered the rate of muscle relaxation without changing peak twitch force. These results illustrate the feasibility of acute, optomechanical manipulation of cardiomyocyte contraction and suggest that this approach could be used to probe the dynamic behavior of the cardiac sarcomere without altering its intrinsic properties. Other experimentally meaningful stimulus protocols could be designed by making use of the optomechanical cardiomyocyte model presented here.
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5.
Increased hs-CRP and decreased 1,25-dihydroxyvitamin D are associated with increased left ventricle lead threshold.
Gözübüyük, G, Koç, M, Kaypaklı, O, Şahin, DY
Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing. 2016;(2):177-183
Abstract
PURPOSE There are not enough data about threshold changes in patients with CRT. In this study, we aimed to investigate frequency of significant threshold increase of left ventricle lead and to determine clinical, demographic, medical and laboratory parameters that associated with threshold increase in CRT implanted patients. METHODS We included CRT implanted 200 patients (124 males, 76 females; mean age 65.8 ± 10.3 years) to this study. Basal and third month LV R wave amplitude, electrode impedance, and threshold values were recorded. Threshold increase was accepted as ≥0.1 V and significant increase as >1 V. Patients were divided into two groups: increased threshold and non-increased threshold for LV lead. RESULTS Number of patients with increased LV threshold was 68 (37.6 %). Furthermore, 8 % of patients had severe increase (≥1 V) in LV threshold. We observed that serum levels of hs-CRP and 1,25 (OH)2 vitamin D were independently associated with increased LV threshold. We showed that 1 mg/dl increase in hs-CRP and the 1 mg/dl decrease in vitamin D are associated with 25.3 and 4.5 % increase in the odds of increased LV threshold, respectively. CONCLUSIONS Increased hs-CRP and decreased 1,25 (OH)2 vitamin D are the strongest predictors of increased LV lead thresholds. We suggest that hs-CRP and 1,25 (OH)2 vitamin D may be used as markers to predict and follow the patients with increased thresholds. It may be useful to finalize CRT procedure with more appropriate basal threshold in patients with high serum hs-CRP and low 1,25 (OH)2 vitamin D levels.
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Relative refractoriness of left ventricular contraction underlies human tachycardia-induced mechanical and electrical alternans.
Kashimura, T, Kodama, M, Watanabe, T, Tanaka, K, Hayashi, Y, Ohno, Y, Obata, H, Ito, M, Hirono, S, Hanawa, H, et al
Pacing and clinical electrophysiology : PACE. 2014;(2):197-206
Abstract
BACKGROUND Mechanical alternans (MA) and electrical alternans (EA) are predictors of cardiac events. Experimental studies have suggested that refractoriness of calcium cycling underlies these cardiac alternans. However, refractoriness of left ventricular contraction has not been examined in patients with cardiac alternans. METHODS In 51 patients with miscellaneous heart diseases, incremental right atrial pacing was performed to induce MA and EA. MA was quantified by alternans amplitude (AA: the difference between left ventricular dP/dt of a strong beat and that of a weak beat), and AA at 100/min (AA100) and maximal AA (AAmax) were measured. EA was defined as alternation of T wave morphology in 12-lead electrocardiogram. Relative refractoriness of left ventricular contraction was examined by drawing the mechanical restitution curve under a basal coupling interval (BCL) of 600 ms (100/min) and was assessed by the slope at BCL (Δmechanical restitution). Postextrasystolic potentiation (PESP) was also examined and the slope of PESP curve (ΔPESP) was assessed as a property to alternate strong and weak beats. RESULTS MA and EA were induced in 19 patients and in none at 100/min or less, and at any heart rate in 32 and in 10, respectively. AA100 and AAmax correlated positively with Δmechanical restitution and negatively with ΔPESP. Patients with EA had a significantly larger Δmechanical restitution and a significantly larger absolute value of ΔPESP than those without. CONCLUSIONS In patients with MA and EA, the left ventricular contractile force during tachycardia is under relative refractoriness and prone to cause large fluctuation of contractile force.
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Application of rapid artificial cardiac pacing in thoracic endovascular aortic repair in aged patients.
Chen, J, Huang, W, Luo, S, Yang, D, Xu, Z, Luo, J
Clinical interventions in aging. 2014;:73-8
Abstract
OBJECTIVE To compare the safety, efficacy, and impact on stent graft positioning between rapid artificial cardiac pacing (RACP), induced hypotension and sodium nitroprusside (SNP) induced hypotension during thoracic endovascular aortic repair (TEVAR) for Stanford B aortic dissection. METHODS One hundred and sixty-eight patients, who were diagnosed with Stanford B aortic dissection and who underwent selective TEVAR in Guangdong General Hospital and the People's Hospital of Baoan District, Shenzhen, People's Republic of China, were enrolled in this study. Patients were randomly divided into a RACP group (n=77) and a SNP group (n=91). During localization and deployment of the stent graft, hypotension was induced by RACP or intravenous SNP, according to randomization. Hemodynamics, landing precision (deviation from planned placement site), duration of procedure, renal function, neurocognitive function, and incidence of endoleaks and paraplegia/hemiplegia were compared. Except for methods of inducing hypotension, TEVAR was performed according to the same protocol in each group. RESULTS RACP was successfully performed in all patients assigned to the RACP group. Compared with the SNP group, blood pressure was significantly lower (43±5 versus 81±6 mmHg, P=0.003) and the restoration time of blood pressure and the operation duration were significantly shorter (7±2 versus 451±87 seconds, P<0.001; 87±15 versus 106±18 minutes, P<0.001, respectively) in the RACP group. Stent graft localization/deployment was more precise in the RACP group (2±1 versus 5±2 mm, P<0.001). Compared to baseline, there was no significant change after TEVAR in either group in regard to renal function, neurocognitive function, and incidence of endoleaks and paraplegia/hemiplegia. CONCLUSION RACP can be safely applied to patients undergoing TEVAR for Stanford B dissection. RACP can shorten the operation duration and facilitate precise graft localization/deployment.
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Are plasma natriuretic peptide levels influenced by automatic pacemaker algorithms for ventricular pacing minimization?
Kreuzer, J, Lennerz, C, Dietl, JU, Beier, T, Strauch, A, Semmler, V, Badran, H, Zrenner, B, Kolb, C
Pacing and clinical electrophysiology : PACE. 2013;(4):424-32
Abstract
BACKGROUND Automatic atrioventricular search hysteresis (AVSH) is designed to reduce the cumulative percentage of potentially deleterious right ventricular apical pacing (VP%) in dual-chamber pacemakers. We investigated whether minimizing VP% by AVSH can, in turn, reduce ventricular wall stretching/stress, as assessed by plasma concentrations of the amino-terminal fragment of the pro-B-type natriuretic peptide (NT-proBNP). METHODS After dual-chamber pacemaker implantation in 81 patients (age: 69 ± 11 years; males: 55.6%), the fixed atrioventricular delay of 225 ms was programmed and AVSH was turned off for 1 month. The patients were thereafter randomly assigned to standard AVSH for 1 month, followed by an enhanced AVSH for another month, or vice versa. At the 1-, 2-, and 3-month follow-ups, VP% values were retrieved from the pacemaker memory, and venous blood samples were taken for NT-proBNP measurements. RESULTS Both standard and enhanced AVSH reduced the median VP% value from 38.5% (for the fixed atrioventricular delay) to 2.1% (P < 0.001). However, plasma NT-proBNP concentrations for the fixed atrioventricular delay (median, 253 pg/mL), standard AVSH (225 pg/mL), and enhanced AVSH (276 pg/mL) did not differ significantly on the intrapatient basis (paired Wilcoxon tests) between any pair of these modalities. CONCLUSION Minimizing ventricular pacing by AVSH during 1 month had no influence on plasma NT-proBNP levels (i.e., ventricular wall stretching/stress) compared with a constant, moderately prolonged atrioventricular delay.
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9.
[A randomized controlled trial of rapid artificial cardiac pacing in thoracic endovascular aortic repair].
Huang, WH, He, PC, Luo, JF, Liu, Y, Chen, JY, Tan, N, Zhou, YL
Zhonghua yi xue za zhi. 2011;(24):1668-72
Abstract
OBJECTIVE To compare the safety, efficacy and their impact on stent graft positioning between rapid artificial cardiac pacing induced hypotension and sodium nitroprusside induced hypotension during thoracic endovascular aortic repair (TEVAR). METHODS From September 2007 to February 2009, a randomized controlled trial as approved by the Ethics Committee of our hospital was conducted in 197 patients undergoing elective thoracic endovascular aortic repair of thoracic aortic dissection (n = 175) or aneurysm (n = 22). The patients were randomized into sodium nitroprusside group (n = 98) and rapid artificial cardiac pacing group (n = 99). During the localization and deployment of stent graft, hypotension was induced by intravenous sodium nitroprusside or rapid artificial cardiac pacing. Hemodynamics, landing precision (deviation from planned placement site), duration of procedure, renal function, neurocognitive function, incidence of endoleaks and paraplegia/hemiplegia were compared. RESULTS Rapid artificial cardiac pacing was conducted without technical difficulty in all 99 patients. The level of hypotension (mm Hg, 1 mm Hg = 0.133 kPa) was most pronounced in the rapid artificial cardiac pacing group (47 ± 5 vs 82 ± 7, P = 0.003. Once rapid pacing ceased, blood pressure recovered more quickly to the preparing levels in the rapid artificial cardiac pacing group [(9 ± 2) s vs (481 ± 107) s, P < 0.01]. And the duration of procedure was also shorter in the rapid artificial cardiac pacing group [(94 ± 16) min vs (103 ± 24) min, P < 0.01]. Moreover, precise positioning and deployment was observed in rapid artificial cardiac pacing group versus to the sodium nitroprusside group (P < 0.01). There was no difference in renal function and neurocognitive function before and after the procedure in both groups. There was no difference in the incidences of endoleaks and paraplegia/hemiplegia between different groups (P > 0.05). CONCLUSION As compared with sodium nitroprusside, rapid artificial cardiac pacing is safer in thoracic endovascular aortic repair. It shortens the endovascular procedure and enables more precise positioning and deployment of stent graft.
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10.
Reduction of right ventricular pacing in patients with sinus node dysfunction through programming a long atrioventricular delay along with the DDIR mode.
Nitardy, A, Langreck, H, Dietz, R, Stockburger, M
Clinical research in cardiology : official journal of the German Cardiac Society. 2009;(1):25-32
Abstract
BACKGROUND Right ventricular (RV) pacing increases the incidence of atrial fibrillation (AF) and hospitalization rate for heart failure. Many patients with sinus node dysfunction (SND) are implanted with a DDDR pacemaker to ensure the treatment of slowly conducted atrial fibrillation and atrioventricular (AV) block. Many pacemakers are never reprogrammed after implantation. This study aims to evaluate the effectiveness of programming DDIR with a long AV delay in patients with SND and preserved AV conduction as a possible strategy to reduce RV pacing in comparison with a nominal DDDR setting including an AV search hysteresis. METHODS In 61 patients (70 +/- 10 years, 34 male, PR < 200 ms, AV-Wenckebach rate at > or =130 bpm) with symptomatic SND a DDDR pacemaker was implanted. The cumulative prevalence of right ventricular pacing was assessed according to the pacemaker counter in the nominal DDDR-Mode (AV delay 150/120 ms after atrial pacing/sensing, AV search hysteresis active) during the first postoperative days and in DDIR with an individually programmed long fixed AV delay after 100 days (median). RESULTS With the nominal DDDR mode the median incidence of right ventricular pacing amounted to 25.2%, whereas with DDIR and long AV delay the median prevalence of RV pacing was significantly reduced to 1.1% (P < 0.001). In 30 patients (49%) right ventricular pacing was almost completely (<1%) eliminated, n = 22 (36%) had >1% <20% and n = 4 (7%) had >40% right ventricular pacing. The median PR interval was 161 ms. The median AV interval with DDIR was 280 ms. CONCLUSIONS The incidence of right ventricular pacing in patients with SND and preserved AV conduction, who are treated with a dual chamber pacemaker, can significantly be reduced by programming DDIR with a long, individually adapted AV delay when compared with a nominal DDDR setting, but nonetheless in some patients this strategy produces a high proportion of disadvantageous RV pacing. The DDIR mode with long AV delay provides an effective strategy to reduce unnecessary right ventricular pacing but the effect has to be verified in every single patient.