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Biomedical subjects

Scott Sakaguchi

Publications and source records attributed to Scott Sakaguchi.

11 recordsLinked to original sources
PubMed2005

Comparison of ventricular arrhythmia frequency in patients with ischemic cardiomyopathy versus nonischemic cardiomyopathy treated with implantable cardioverter defibrillators.

Implantable cardioverter defibrillators have been shown to provide similar survival benefits for patients who have left ventricular dysfunction due to ischemic heart disease and for subsets of patients who have nonischemic cardiomyopathy. Findings in this study extend these observations by showing that patients who have ischemic or nonischemic heart disease and receive implantable cardioverter defibrillators not only have comparable mortality rates but also similar tachyarrhythmia frequencies during follow-up; further, mortality and tachyarrhythmia outcomes are independent of initial arrhythmia indication.

Adult↗
PubMed2004

Comparison of catecholamine response during tilt-table-induced vasovagal syncope in patients <35 to those >65 years of age.

This study compared alterations in arterial catecholamine concentrations associated with tilt-induced vasovagal syncope that differed in older (>65 years) and younger patients (<35 years). Older patients with tilt-positive tests tended to exhibit higher baseline epinephrine (E) concentrations and lesser E surge before development of syncope than younger patients (<35 years), whereas both groups manifested comparable norepinephrine (NE) responsiveness.

Adult↗
PubMed2004

Syncope.

Syncope is a syndrome consisting of a relatively short period of temporary and self-limited loss of consciousness caused by transient diminution of blood flow to the brain (most often the result of systemic hypotension). Syncope comprises part of a subset of clinical conditions in which loss of consciousness is transient. Other conditions in this group, which are not syncope and should be clearly distinguished from syncope, include, for example, seizure disorders, posttraumatic loss of consciousness, and cataplexy. Recent surveys indicate that syncope accounts for approximately 1% of emergency department visits in Europe, although older reports from the United States placed this number closer to 3%. The reported prevalence of syncope in the population varies: 15% of children before the age of 18 years; 25% of a military population aged 17 to 26 years; 16% and 19%, respectively, in men and women aged 40 to 59 years; and up to 23% in a nursing home population older than 70 years. The highest frequency of syncope occurs in patients with cardiovascular comorbidity and older patients in institutional care settings. The causes of syncope are numerous and, not infrequently, multiple factors may contribute. The diagnostic evaluation is benefited by availability of a detailed medical history and reports of eyewitnesses. In this context, the physician must consider the classification of the causes of syncope, and address the most likely causes first. The principal groups of causes may be summarized as: (1) neurally mediated reflex syncope (eg, vasovagal faint, carotid sinus syndrome); (2) orthostatic (postural) syncope; (3) cardiac arrhythmias; (4) structural cardiac and pulmonary causes; and (5) cerebrovascular disorders (rare). In addition, conditions that may mimic syncope but are not true syncope (eg, psychogenic pseudosyncope) must be considered. Only after a definitive cause is established can appropriate treatment be initiated. In this regard, the syncope evaluation is facilitated by maintaining an organized diagnostic approach. The practitioner should avoid wasteful use of short-term ambulatory electrocardiographic recordings (eg, Holter monitors) and rarely positive neurologic tests (eg, electroencephelography, head magnetic resonance imaging/computed tomography) in the absence of head trauma or evident neurologic signs. In many medical centers the evaluation of patients with syncope is haphazard, and may be substantially enhanced by establishment of a multidisciplinary syncope evaluation unit or team.

Diagnosis, Differential↗
PubMed2004

Transient modification of baroreceptor response during tilt-induced vasovagal syncope.

AIMS: Normally, arterial baroreceptors attempt to minimize systemic hypotension by initiating reflex vasoconstriction and tachycardia. However, in the setting of vasovagal syncope (VVS), these usual compensatory mechanisms either fail to be triggered or the response is inadequate. We hypothesized that in VVS prone individuals, arterial baroreceptor response (BRR) is normal under most conditions, but that a transient functional BRR disturbance occurs during an evolving vasovagal faint and may in part account for failure of the usual compensatory response. METHODS AND RESULTS: This study assessed BRR in the baseline state and again in association with either VVS induced head-up tilt (HUT) or after a prolonged period of upright posture without VVS. To minimize impact on HUT outcome, BRR was estimated non-pharmacologically by measuring blood pressure and heart rate changes, induced when subjects were returned to the supine position after undergoing diagnostic 70 degrees HUT evaluation. Beat to beat heart rate and arterial blood pressure changes were recorded in 13 patients with syncope and another 16 individuals with negative HUT (control group). Baseline BRR was initially evaluated at the end of a 3 min symptom free HUT (HUT#1), and the measurement was repeated after a 45 min duration HUT in the control group or in conjunction with syncope in VVS prone individuals (HUT#2). Baseline BRR did not differ significantly in controls and VVS prone individuals (controls: 3.37+/-1.56, VVS prone: 6.0+/-2.02 ms/mmHg, p=0.27). Further, at the end of 45 min HUT#2, BRR was unaltered from baseline in control subjects (4.92+/-1.36 ms/mmHg, p=0.48), but was markedly reduced from baseline value in individuals who experienced a faint, -3.30+/-0.81 ms/mmHg (p<0.0003 vs baseline). CONCLUSION: Compared with individuals who do not manifest VVS during HUT, VVS prone individuals appear to demonstrate functional diminution of baroreceptor responsiveness. This altered response may undermine the normal expected compensatory response to evolving systemic hypotension. The basis for this transient disturbance in baroreceptor responsiveness is currently unknown.

Aged↗
PubMed2004

Impact of age and blood pressure on the lower arterial pressure limit for maintenance of consciousness during passive upright posture in healthy vasovagal fainters: preliminary observations.

Maintenance of consciousness importantly depends on systemic arterial blood pressure (BP) remaining above the lower pressure limit for cerebrovascular autoregulation. This study evaluated the impact of age and baseline arterial blood pressure (BP) on the BP recorded at onset of syncope in otherwise healthy individuals undergoing passive head-up tilt (HUT) testing for suspected vasovagal syncope. Since hypertension is thought to shift the lower autoregulation point to higher values, and since older healthy patients tend to have higher BP than younger individuals, we hypothesized that even among healthy individuals HUT-induced syncope would occur at higher BP in older compared with younger subjects. Three groups of otherwise healthy individuals who had positive HUT were identified: Group 1: <25 years, n=17; Group 2: 25-59 years, n=18; and Group 3: > or =60 years, n=7. As expected, baseline arterial systolic blood pressure of patients > or =60 years (162+/-37 mmHg) was significantly higher than in the other two groups (Group 1: <25 years, 116+/-15 mmHg; Group 2: 25-59 years, 128+/-12 mmHg). Further, the > or =60 age group tolerated upright posture for a longer period before syncope than did younger patients. However, despite a trend for BP at syncope to increase with age, differences were small (Group 3: > or =60 years, 61+/-15 mmHg, Group 2: 25-59 years, 58+/-6 mmHg, and Group 1: 54+/-16 mmHg) and were not statistically significant. Thus, in generally healthy individuals, age and baseline BP has only a minor effect on the lower limit of BP necessary for maintenance of consciousness. On the other hand, higher baseline BP provides older individuals a greater blood pressure 'reserve' for maintenance of consciousness compared with younger subjects.

Adolescent↗
PubMed2004

Biventricular implantable cardioverter defibrillators improve survival compared with biventricular pacing alone in patients with severe left ventricular dysfunction.

INTRODUCTION: Biventricular cardiac pacemakers provide important hemodynamic benefit in selected patients with heart failure and severe left ventricular (LV) dysfunction. Nevertheless, these patients remain at high mortality risk. To address this issue, we examined mortality outcome in patients with heart failure treated with biventricular pacemakers alone and those treated with biventricular implantable cardioverter defibrillators (ICDs). METHODS AND RESULTS: The study population consisted of 126 consecutive patients with LV dysfunction and heart failure who received either a biventricular ICD (n = 62) or a biventricular pacemaker (n = 64) between January 1998 and December 2002. A minimum 12 months of follow-up was obtained in all survivors. ICD indications were conventional in all patients. Kaplan-Meier actuarial method and log rank statistics were used to calculate and compare survival rates in both groups. Comparison of mortality rates utilized Chi-square test. The two groups had similar clinical and demographic features, LV ejection fraction, and medication use. Average follow-up times were 13 +/- 11.8 months (range 4-60) and 18 +/- 13.2 months (range 0.5-53) for biventricular ICD and pacemaker groups, respectively. Overall mortality rate was significantly lower in the biventricular ICD group (13%, 8 deaths) compared to the pacemaker group (41%, 26 deaths) (P = 0.01). Further, the predominant survival benefit for ICD-treated patients becomes evident after the first 12 months of follow-up. CONCLUSION: The findings in this study, although necessarily limited in their interpretation by the absence of treatment randomization, suggest that biventricular ICDs offer a survival benefit compared to biventricular pacing alone. Furthermore, this benefit may be most apparent if other clinical factors do not preclude patient survival >1 year postimplant.

Aged↗
PubMed2003

Comparison of automatic and patient-activated arrhythmia recordings by implantable loop recorders in the evaluation of syncope.

The implantable loop recorder (ILR) has become an important tool for evaluating patients with recurrent syncope. Second generation ILRs have the ability to record events either automatically (auto activated) or by manual activation (patient activated). In an attempt to evaluate the relative utility of the auto-activation feature, this study stratified ILR events based on a grading system designed to classify detected arrhythmias in terms of the likelihood that they provide a diagnostic basis for syncope. Data from 50 patients (27 men, mean age 64 +/- 22 years) who underwent ILR implantation for investigation of recurrent syncope were assessed. The arrhythmia syncope grading system used 5 levels, ranging from grade 0 (rhythm recorded during syncope) to grade IV (rhythm unlikely to provide a diagnostic basis for syncope). Thirty-six patients (72%) demonstrated > or =1 auto-activated or patient-activated recording during a follow-up of 14.3 +/- 7.9 months. Of the total of 529 recordings, 223 (194 after auto activation [86.9%]) from 30 patients showed a rhythm abnormality. Auto activation was more effective for documenting arrhythmias that were recorded during syncope or those with highest probability of providing a syncope diagnosis (grade 0 or I arrhythmias: auto activated, 19 patients, patient activated, 3 patients). Times from ILR implantation to first grade 0 and grade I arrhythmias were 13.4 and 7.8 months, respectively. The ILR auto-activation feature proved effective in providing a high probability basis for syncope (196 arrhythmia recordings [87.1%] in 27 patients) and enhanced the diagnostic effectiveness of the device compared with patient activation alone (29 arrhythmia recordings [12.9%] in 6 patients).

Arrhythmias, Cardiac↗
PubMed2003

Implantable diagnostic monitoring devices for evaluation of syncope, and tachy- and brady-arrhythmias.

Symptoms arising from cardiac arrhythmias are often transient. Consequently, defining the responsible rhythm disturbance remains a challenge. However, absent a confident diagnosis of the arrhythmic basis for the symptoms, it is not possible to develop an effective treatment strategy. The implantable loop recorder (ILR) has become a valuable element in the evaluation of patients with suspected intermittent arrhythmia related symptoms. In this regard, clinical studies have not only demonstrated its superior effectiveness compared to other monitoring modalities, but even suggest that it may be cost-effective for the ILR to be used at an earlier stage of the evaluation strategy.

Bradycardia↗
PubMed2003

Improved survival of cardiac transplantation candidates with implantable cardioverter defibrillator therapy: role of beta-blocker or amiodarone treatment.

INTRODUCTION: Survival in patients awaiting cardiac transplantation is poor due to the severity of left ventricular dysfunction and the susceptibility to ventricular arrhythmia. The potential role of implantable cardioverter defibrillators (ICDs) in this group of patients has been the subject of increasing interest. The aims of this study were to ascertain whether ICDs improve the survival rate of patients on the waiting list for cardiac transplantation and whether any improvement is independent of concomitant beta-blocker or amiodarone therapy. METHODS AND RESULTS: Data comprised findings from 310 consecutive patients at a single center who were evaluated and deemed suitable for cardiac transplantation and placed on the waiting list. Kaplan-Meier actuarial approach was used for survival analysis. Survival analysis censored patients at time of transplantation or death. Of the 310 patients, 111 (35.8%) underwent successful cardiac transplantation and 164 (52.9%) died while waiting; 35 patients remain on the waiting list. Fifty-nine (19%) patients had ICD placement for ventricular arrhythmias prior to or after being listed. Twenty-nine (49.1%) ICD patients survived until cardiac transplantation, 13 (22%) patients died, and 17 (28.8%) remain on the waiting list. Among non-ICD patients, 82 (32.7%) received transplants, 151 (60.2%) died, and 18 (7.2%) remain on the waiting list. Survival rates at 6 months and 1, 2, 3, and 4 years were better for all ICD patients compared to non-ICD patients (log-rank x2, P = 0.0001). By multivariate analysis, ICD therapy and beta-blocker treatment were the strongest predictors of survival. Further, ICD treatment was associated with improved survival independent of concomitant treatment with beta-blocker or amiodarone. Among ICD and non-ICD patients treated with a beta-blocker or amiodarone, survivals at the 1 and 4 years were 93% vs 69% and 57% vs 32%, respectively (log-rank x2, P = 0.003). CONCLUSION: ICD therapy is associated with improved survival in high-risk cardiac transplant candidates, and ICD benefit appears to be independent of concomitant treatment.

Adrenergic beta-Antagonists↗