Thesis (M.S.)--University of Wisconsin--Madison, 1985. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 168-174).

Cardiac pacing has been the only effective treatment in the management of patients with symptomatic bradycardia caused by sinus node dysfunction or atrioventricular block for decades. Conventional dual-chamber pacing is performed by implanting two leads in right atrial (RA) appendage and right ventricular (RV) apex separately. RV apex is the most commonly applied pacing site because it can be easily reached and allows a chronically stable position and stimulation thresholds. However, large randomized clinical trials have suggested that right ventricular apical (RVA) pacing may cause abnormal ventricular contraction and reduce pump function and lead to myocardial hypertrophy, in particular in patients with impaired left ventricular (LV) function. Recent studies have also reported a reduced LV systolic function in patients with pacing indications and preserved ejection fraction. The deleterious effects of RVA pacing on LV function may be related to the abnormal electrical and mechanical activation pattern or ventricular dyssynchrony. During RVA pacing, conduction of the electrical wave front propagates slowly through ventricular myocardium rather than through the His-Purkinje conduction system, comparable to left bundle branch block (LBBB). In addition , RVA pacing alters ventricular synchrony and loading conditions which may result in diastolic heart failure with abnormal LV relaxation, high filling pressure and low cardiac output state. Furthermore, it is possible that left atrial (LA) remodeling and reduction of atrial function may occur during RVA pacing . However, it is not been carefully studied. / Echocardiography is a convenient, non-invasive and established tool to assess cardiac function in clinical practice. Conventional two-dimensional echocardiography is useful to assess cardiac chamber size, volume and function. With the development of real time three-dimensional echocardiography (RT3DE) and color tissue Doppler imaging (TDI), echocardiography provides further valuable information and more accurate measurements which include myocardial velocity and parameters of dyssynchrony. In the present study, the main echocardiographic parameters including the maximal left atrial volume (LAVmax), pre-atrial contraction volume (LAVpre) and the minimal left atria l volume (LAVmin) were assessed by two-dimensional echocardiography. Peak systolic (Sm-la), peak early diastolic (Em-la), peak late diastolic (Am-la) velocities of left atrium (LA) and atrial conduction time (from onset of P wave on electrocardiogram to onset of atrial velocity) were measured by TDI. / In a cross-sectional study, ninety-eight patients who had been implanted with RVA-based dual-chamber pacemakers were enrolled. Four patients with pacing dependent were excluded. Eventually 94 patients were included in the final analysis. Echocardiography was performed (iE33, Philips) during intrinsic ventricular conduction (V-sense) and RVA pacing (V-pace) modes with 15 minutes between switching modes. We aimed to investigate if RVA pacing has any acute effects on atrial remodeling and function in patients with preserved ejection fraction (LV ejection fraction> 45%). The result showed that during V-pace, LA volumes increased significantly when compared with V-sense (LAVmax: 52.0 +/- 18.8 vs. 55.2 +/- 21.1 ml, p = 0.005; LAVpre: 39.8 +/- 16.4 vs. 41.3 +/- 16.6 ml, p = 0.014; LAVmin: 27.4 +/- 14.0 vs. 29.1 +/- 15.1 ml, p = 0.001) . TDI parameters showed significant reduction in Sm-la (3.0 +/- 1.1 vs. 2.7 +/- 0.9 cm/s, p < 0.01), Em-la (2.7 +/- 1.1 vs. 2.4 +/- 1.0 cm/s, p = 0.001). However, there was no change in Am-la. / In a prospective study, patients with symptomatic bradycardia, preserved ejection fraction, and received RVA pacing were recruited. Echocardiography was performed at both baseline and one year follow up through a standard protocol by experienced echocardiographers. LA volumes and velocities as well as intra- and interatrial dyssynchrony were measured offline with the use of dedicated software. The objectives of this study were to investigate: (1) if RVA pacing has any deleterious effects on LA remodeling and function during long-term follow up; (2) if RA appendage pacing has separate effects on atrial pump function, intra- and interatrial dyssynchrony; (3) if atrial dysfunction and dyssynchrony can predict atrial high rate episodes (AHREs) burden in the first year of RVA pacing. The main findings of this study were: (a) at one year follow up, LA volumes and indexes were increased with reduction in passive emptying fraction and total emptying fraction. Atrial velocities showed significant reduction when compared with baseline; (b) in multivariate regression analysis, the ratio of transmitral early diastolic filling velocity to mitral annular early diastolic velocity (E/e') > 15 at one year and reduction of LV ejection fraction ≥ 5% were independent predictors of reduction of Am-la > 30%; (c) high percent of RA appendage pacing prolonged atrial conduction and induced intra- and interatrial dyssynchrony. (d) Am-la < 5.3 cm/s can predict AHREs burden which had a sensitivity of 71% and specificity of 75%. / In conclusion, our studies suggest even short-term RVA pacing induces LA dilatation and impaired passive atrial function, though it did not have direct effect on active atrial contractility. However, chronic RVA pacing results in LA remodeling and reduces atrial function with decreased contractility. This was more likely to occur in those with impaired LV ejection fraction and evidence of diastolic dysfunction. Atrial dysfunction and interatrial dyssynchrony can predict AHREs burden after chronic RVA pacing. Therefore, measures that may minimize such adverse effect of pacing on atrial function need to considered for patients receiving RVA pacing, such as the use of new pacing modalities. / Xie, Junmin. / "December 2010"--Abstract. / Adviser: Yu Cheuk Man. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 142-161). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Reviews of clinical practice for paediatric pacemaker implantation and follow-up are necessary to provide an evidence-base for future policy and practice in this field. Epicardial pacing data available through Green Lane Hospital, New Zealand's (NZ) primary referral centre for paediatric cardiac surgery and pacemaker implantation, was reviewed with the following aims: Assessment of pacemaker lead performance over time in relation to the type of epicardial lead implanted - steroid-eluting (SE) and non steroid-eluting (NSE). Determination of the survival rate of epicardial leads. Identifying factors predicting or associated with lead failure.A database of pacing and sensing thresholds and lead impedance data at implant, 2, 6 and 18 weeks and 6 monthly intervals thereafter, was compiled and the prevalence and timing of complications in relation to lead type, location and implant route determined. In total 192 leads (155 SE, 37 NSE) were implanted in 96 patients (52 male) aged 3 days to 71 years (y) (median 1.7y), 74 patients were < 17 years of age at implant. Congenital heart defects were present in 82% of patients. Follow-up (f/u) was possible for 180 leads. Mean f/u duration for the 150 SE leads was 3.1y (2 weeks - 8.8y) and for the 30 NSE leads was 4.5y (2 weeks - 27y).SE and NSE pacing thresholds were similar at implant. NSE pacing thresholds peaked at 6 weeks post implant and remained significantly higher than SE leads throughout f/u in surviving leads, although the difference was small at 2 and 4 y. SE and NSE leads had similar ventricular sensing thresholds and lead impedances throughout the study period.Survival at 5 years for all leads was 61% (66% for SE leads and 41% for NSE leads). Primary causes of failure in the leads receiving f/u were exit block and lead fracture. The occurrence of exit block was significantly higher (p<0.0001) in NSE leads (57%) compared to SE leads (5%). Lead fracture occurred in 15% of leads with the highest fracture rate at 2-3 y post implant. Patient age and weight at implant, gender, previous cardiac surgery, lead polarity, indication for pacing and implant route were not predictors of lead failure. NSE leads were 6 times more likely to fail compared to SE leads (p <0.0001).The main study findings were: SE leads maintain lower pacing thresholds and a reduced incidence of exit block compared to NSE leads. It is therefore recommended that SE leads be developed which can penetrate fibrosed, scarred or fatty epicardial surfaces. Where SE lead use is contraindicated, alternative surgical techniques for SE lead placement should be attempted rather than implanting NSE leads. Lead fracture is a significant complication of epicardial pacing in paediatric patients. Using stronger bipolar leads implanted by the subxiphoid route may reduce the risk of fracture. Medium term survival (5 y) of SE epicardial leads is acceptable and therefore the continued use of these leads is recommended, particularly in young patients, allowing their veins to be saved for transvenous leads later in their life.

Reviews of clinical practice for paediatric pacemaker implantation and follow-up are necessary to provide an evidence-base for future policy and practice in this field. Epicardial pacing data available through Green Lane Hospital, New Zealand's (NZ) primary referral centre for paediatric cardiac surgery and pacemaker implantation, was reviewed with the following aims: Assessment of pacemaker lead performance over time in relation to the type of epicardial lead implanted - steroid-eluting (SE) and non steroid-eluting (NSE). Determination of the survival rate of epicardial leads. Identifying factors predicting or associated with lead failure.A database of pacing and sensing thresholds and lead impedance data at implant, 2, 6 and 18 weeks and 6 monthly intervals thereafter, was compiled and the prevalence and timing of complications in relation to lead type, location and implant route determined. In total 192 leads (155 SE, 37 NSE) were implanted in 96 patients (52 male) aged 3 days to 71 years (y) (median 1.7y), 74 patients were < 17 years of age at implant. Congenital heart defects were present in 82% of patients. Follow-up (f/u) was possible for 180 leads. Mean f/u duration for the 150 SE leads was 3.1y (2 weeks - 8.8y) and for the 30 NSE leads was 4.5y (2 weeks - 27y).SE and NSE pacing thresholds were similar at implant. NSE pacing thresholds peaked at 6 weeks post implant and remained significantly higher than SE leads throughout f/u in surviving leads, although the difference was small at 2 and 4 y. SE and NSE leads had similar ventricular sensing thresholds and lead impedances throughout the study period.Survival at 5 years for all leads was 61% (66% for SE leads and 41% for NSE leads). Primary causes of failure in the leads receiving f/u were exit block and lead fracture. The occurrence of exit block was significantly higher (p<0.0001) in NSE leads (57%) compared to SE leads (5%). Lead fracture occurred in 15% of leads with the highest fracture rate at 2-3 y post implant. Patient age and weight at implant, gender, previous cardiac surgery, lead polarity, indication for pacing and implant route were not predictors of lead failure. NSE leads were 6 times more likely to fail compared to SE leads (p <0.0001).The main study findings were: SE leads maintain lower pacing thresholds and a reduced incidence of exit block compared to NSE leads. It is therefore recommended that SE leads be developed which can penetrate fibrosed, scarred or fatty epicardial surfaces. Where SE lead use is contraindicated, alternative surgical techniques for SE lead placement should be attempted rather than implanting NSE leads. Lead fracture is a significant complication of epicardial pacing in paediatric patients. Using stronger bipolar leads implanted by the subxiphoid route may reduce the risk of fracture. Medium term survival (5 y) of SE epicardial leads is acceptable and therefore the continued use of these leads is recommended, particularly in young patients, allowing their veins to be saved for transvenous leads later in their life.

The effect of CRT on incidence of AF development in patients with severe HF was explored by comparing 36 patients with conventional indication for the CRT to 36 HF patients without CRT, matched for age, sex and LV systolic function (Publication 5). After a follow up of 3 years, the annual incidence of AF in the CRT group was 2.8%, which was significantly lower than the control group (10.2%). Moreover, the echocardiographic benefit by CRT was compared between these 36 patients with SR and 15 patients with persistent AF. The results showed that the echocardiographic response was similar between the two groups. These findings suggested that CRT may have the potential to reduce AF burden in patients with severe HF and that patients with persistent AF may also benefit from CRT. / The objective of the study (Publication 1) was to assess the feasibility of using non-contact LV mapping to delineate the LV endocardial activation pattern in 7 HF patients in NYHA class III, with low LVEF and wide QRS complex (>120ms). Non-contact mapping was safely performed and there were two endocardial conduction patterns identified, namely homogenous (Type I) and conduction block (Type II). The second part of the study (Publication 2) was to determine the implication of these two distinct activation patterns to echocardiographic and clinical response to CRT. 23 patients in NYHA class III, with LVEF &lt;35% and QRS duration >120ms were recruited in this study. 15 patients had Type II pattern and 8 Type I. The QRS duration between the two types of conduction patterns were comparable. Patients with Type II pattern had a more favourable echocardiographic and clinical response to CRT than those with Type I. It was concluded that, despite the similar QRS duration between the two types of LV endocardial activation patterns, patients with Type II pattern had a more favourable response to CRT. / The significance of baseline renal function in CRT was assessed in 85 consecutive patients with conventional indication for the CRT (Publication 7). There was no significant relationship between baseline renal function and significant LV reverse remodeling after CRT, suggesting baseline renal insufficiency probably would not affect the response to CRT. (Abstract shortened by UMI.) / This study (Publication 3) was to determine the effect of CRT in patients with narrow QRS complex and evidence of mechanical dyssynchrony as determined by TDI. 51 patients in NYHA class III or IV, with LV ejection fraction &lt;35%, and QRS duration &lt;120ms were recruited for the CRT. The effect of the device therapy on LV systolic function in this cohort was compared to 51 patients who fulfilled the current criteria with wide QRS complex. CRT significantly improved the LV systolic function, NYHA class and exercise capacity in those with narrow complex to a similar extent in those with wide complex. With co-existing mechanical dyssynchrony determined by TDI, patients in both narrow and wide QRS complex groups showed more favourable response to CRT than those without significant mechanical dyssynchrony. This confirmed that QRS was a poor marker of mechanical dyssynchrony and the current selection criteria are probably not adequate to include more potential responders to the therapy. / This study (Publication 4) was to determine the role of optimal medical therapy in CRT recipients before implantation. The echocardiographic and clinical effect of CRT in 30 patients without the optimal combination of ACEi or ARB and beta-blockers was compared to 30 patients matched for age, sex, NYHA class and HF etiology. Patients with optimal medical therapy had significantly better echocardiographic and clinical response to CRT. The results confirmed that optimal medical therapy is necessary to achieve maximal response by CRT. / This study (Publication 6) was to determine if patients with moderate LV systolic function and wide QRS complex would benefit from the CRT. Significant improvement in LV systolic function was observed in 15 patients with LVEF between 35 and 45%, NYHA class III and QRS duration >120ms after CRT, suggesting that presence of LV systolic dysfunction and cardiac dyssynchrony may be the major determining factors for favourable CRT response. Therefore, patients with less advanced HF may also benefit from the CRT. / "May 2007." / Adviser: Yu Cheuk Man. / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4657. / Thesis (M.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 133-151). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / School code: 1307.

Diss. (sammanfattning) Stockholm : Tekn. högsk. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 6 uppsatser.

Diss. Linköping : Univ.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 5 uppsatser.

Orientador: Salomon Soriano Ordinola Rojas / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-12T15:05:14Z (GMT). No. of bitstreams: 1 Veiga_VivianeCordeiro_M.pdf: 4383215 bytes, checksum: 4ac235c87c9173ad91395fd7c6466208 (MD5) Previous issue date: 2008 / Resumo: Introdução A terapia de ressincronização cardíaca é uma opção efetiva nos pacientes com insuficiência cardíaca avançada. No entanto, 20 a 30% dos pacientes não apresentam benefícios à esta terapêutica. Critérios clínicos, eletrocardiográficos e ecocardiográficos têm sido estudados na tentativa de selecionar os pacientes que serão beneficiados com a ressincronização cardíaca, sendo o ecocardiograma um método utilizado tanto na seleção, quanto na avaliação e otimização desta terapêutica. Objetivo: O objetivo deste trabalho é analisar a utilização do ecocardiograma na avaliação da terapia de ressincronização cardíaca em pacientes portadores de insuficiência cardíaca refratária, no seguimento a curto prazo (dez dias) e após dois anos de evolução. Casuística e Método: Foram avaliados 20 pacientes com indicação de implante de marcapasso biventricular para terapia de ressincronização cardíaca no período de dois anos, sendo 16 (80%) do sexo masculino, com idade variando de 27 a 80 anos (59,70 ± 12,59 anos). A etiologia da cardiomiopatia era isquêmica em 10 pacientes (50%), chagásica em seis (30%) e idiopática em 4 (20%). Quinze pacientes encontravam-se em classe funcional III (New York Heart Association) e cinco em classe funcional IV no momento do implante do marcapasso. Foi aplicado o Questionário de Qualidade de Vida de Minnesota e realizado o teste de caminhada de seis minutos para avaliação das condições clínicas dos pacientes. Realizado ecodopplercardiograma bidimensional para avaliação da função ventricular, diâmetros cavitários, índice de performance miocárdica, estudo da dissincronia interventricular (avaliação do atraso eletromecânico entre os ventrículos esquerdo e direito) e intraventricular (análise pelo modo unidimensional e Doppler tecidual), da função diastólica e do grau da regurgitação mitral. Dez dias após o implante do marcapasso biventricular, foi repetida toda a avaliação inicial e, novamente, após dois anos. Resultados: Em dois anos, cinco pacientes (25%) foram à óbito, sendo que destes, quatro apresentavam etiologia chagásica. A duração média do complexo QRS era de 154,5±18,48 x 129,0±22,91 x 134,0±24,14 ms, respectivamente nos períodos pré-operatório, dez dias e dois anos de pós-operatório. Não houve alteração estatisticamente significante da fração de ejeção entre os períodos pré-operatório e dez dias, mas houve alteração significante entre os períodos pré-operatório e dois anos e dez dias e dois anos. No seguimento de dez dias, houve piora da dissincronia intraventricular avaliada pelo Doppler tecidual, assim como a pontuação no escore de qualidade de vida foi maior, no grupo óbito. Conclusão: A ecocardiografia é uma tecnologia em evolução e dos parâmetros avaliados, somente a avaliação da dissincronia intraventricular pelo Doppler tecidual após o procedimento, foi capaz de predizer a eficácia da terapia de ressincronização cardíaca, em relação à mortalidade. Não houve correlação entre os parâmetros ecocardiográficos e a melhora clínica de alguns pacientes. / Abstract: Introduction In the cardiac resynchronization therapy is an effective option for patients with advanced heart failure. However, 20 to 30% of patients did not show benefits to this therapy. Clinical criteria, electrocardiography and the echocardiography have been studied in an attempt to select the patients who will benefit from the cardiac resynchronization, and the echocardiogram is a method used in both the selection, as in the evaluation and optimization of this therapy. Objective: The objective of this study is to evaluate the use of echocardiography in the evaluation of patients undergoing cardiac resynchronization therapy for a period of two years. Patients and Methods: We evaluated 20 patients with the implantation of biventricular pacemaker for cardiac resynchronization therapy for over two years, and 16 (80%) males, ranging in age from 27 to 80 years (59.70±12.59 years). The etiology of cardiomyopathy was ischemic in 10 patients (50%), Chagas disease in six (30%) and idiophatic in 4 (20%). Fifteen patients were in functional class III (New York Heart Association) and five in functional class IV at the time of implantation of the pacemaker. We applied the Quality of Life Questionnaire of Minnesota and conducted the test of a six-minute walk to evaluate the clinical conditions of patients. Directed two-dimensional Doppler echocardiography for evaluation of ventricular function, cavity diameters, myocardial performance index, study of interventricular dyssynchrony (eletromechanical delay left ventricle - the right ventricle) and intraventricular (by way dimensional analysis and tissue Doppler), the diastolic function and degree of mitral regurgitation. Ten days after implantation of biventricular pacemaker, was repeated throughout the initial assessment and again after two years. Results: In two years, five patients (25%) were to death, and that these, four had Chagas disease. The average duration of the QRS complex was 154.5±18.48 x 129.0±22.91 x 134.0±24.14 ms, respectively in preoperative, ten days and two years after surgery. There was no statistically significant change in the ejection fraction between preoperative and ten days but there was significant change between periods preoperative and 2 years and 10 days and 2 years. Following ten days, the evaluation of intraventricular dyssynchrony by tissue Doppler and quality of life scores were significantly higher in the group died. Conclusion: The echocardiography is an evolving technology and the parameters evaluated, only the assessment of intraventricular dyssynchrony by Doppler tissue after the procedure was able to predict the effectiveness of the cardiac resynchronization therapy, in relation to mortality. There was no correlation between echocardiographic parameters and clinical improvement in some patients. / Mestrado / Mestre em Cirurgia