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Biomedical subjects

E Rowland

Publications and source records attributed to E Rowland.

At least 19 recordsLinked to original sources
PubMed2003

Comparison between biventricular pacing and single site pacing in patients with poor ventricular function: a hemodynamic study.

Biventricular pacing has been suggested as offering greater hemodynamic benefit than single site pacing in patients with advanced heart failure and left bundle branch block. This was tested using acute multisite pacing. Eighteen such patients were atrialsensed, ventricular multisite paced in random order for 5 minutes. The best achieved measure of cardiac output (CO), pulmonary capillary wedge pressure (PCWP) and left ventricular (LV) + dP/dtmax at RV, LV, and biventricular pacing sites compared. Baseline PCWP, CO, and LV + dP/dtmax were 20 +/- 10 mmHg 4.8 +/- 1.3 L/min and 680 +/- 173 mmHg/s respectively. In all 18 patients CO and in 17 of 18 patients LV + dP/dtmax and PCWP improved with pacing. In the group as a whole, no significant hemodynamic difference between pacing sites was observed in PCWP (pacing site RV 19 +/- 10 mmHg, LV 17 +/- 10, biventricular 18 +/- 11) or CO (RV 5.2 +/- 1.5 L/min, LV 5.1 +/- 1.5, biventricular 5.3 +/- 1.7). Increased stroke volume/PCWP with LV (5.6 +/- 3.7 mLs/mmHg) and biventricular pacing (5.4 +/- 4.0) were not significantly greater compared to RV pacing (4.7 +/- 3.0, ANOVA P = 0.20). Increase in LV + dP/dtmax with pacing at LV (814 +/- 190 mmHg/s) and biventricular (839 +/- 290) sites was not significantly greater than the increase with RV pacing (769 +/- 203 mmHg/s, ANOVA P = 0.30). Pacing in patients with heart failure and conduction delay can produce a hemodynamic benefit. There is individual variation in the pacing site that leads to the greatest improvement. In the group as a whole, biventricular and LV pacing produced only modest improvements compared to RV pacing.

Bundle-Branch Block↗
PubMed2002

Treatment of superior vena cava obstruction secondary to pacemaker wires with balloon venoplasty and insertion of metallic stents.

AIMS: Pacemaker wires can result in stenosis of the superior vena cava and other central veins. The aim of this study is to demonstrate the safety and effectiveness of treating stenoses of the superior vena cava (SVC) and central veins with balloon venoplasty and metallic stent insertion in the presence of cardiac pacemaker wires. METHODS AND RESULTS: Three patients were referred to the department after developing symptomatic SVC obstruction following implantation of a cardiac pacemaker several years earlier. They were examined with duplex ultrasound and venography, which revealed significant stenoses of the central veins. These patients subsequently underwent endovascular treatment which involved balloon dilation and stent insertion. The treatment was successful in all three patients, without any complications. Long-term patency of up to 4 years is recorded. No pacemaker function dysfunction was encountered. CONCLUSION: SVC stenting is safe and effective in patients who develop the SVC obstruction after cardiac pacemaker insertion.

Adult↗
PubMed2002

Effect of multisite pacing on ventricular coordination.

OBJECTIVE: To determine the effect of multisite pacing on left ventricular function. DESIGN: Prospective observational study. PATIENTS: 18 patients with heart failure with a dilated poorly functioning left ventricle (LV) and left bundle branch block. INTERVENTIONS: Pacing for 5 minutes in random order at the right ventricle (RV) apex, RV outflow tract, mid posterolateral LV, RV apex and LV simultaneously, and RV outflow tract and LV simultaneously. The best achieved measurements with RV, LV, and biventricular pacing were compared. MAIN OUTCOME MEASURES: LV dimension, filling characteristics, and long axis indices were measured on echocardiography simultaneously with LV pressure. Cycle efficiency (%)--that is, the ratio of the area of the acquired pressure dimension loop to that of the ideal loop for that segment--quantified coordination. RESULTS: The pacing site that gave the best achieved cycle efficiency differed between patients (biventricular in five, LV in two, RV in seven, and no site in four). In patients with baseline incoordination (cycle efficiency < or = 72%, n = 12) cycle efficiency improved significantly with RV pacing (cycle efficiency 76%, p = 0.01) but not with LV (65%) or biventricular (67%) pacing. LV based pacing induced premature short axis contraction in a subset of patients (n = 4), which was associated with a prolonged time from the Q wave on the ECG to the onset of inward movement of the long axis (from apex to mitral ring): biventricular 145 ms, LV 105 ms, RV 85 ms (biventricular v RV, p < 0.05). Excluding patients with baseline incoordination in whom premature activation occurred, pacing at all sites led to a similar increase in cycle efficiency (RV 78%, LV 72%, biventricular 73%). CONCLUSIONS: Ventricular coordination can be improved with pacing in patients with baseline incoordination. Short and long axis fibres may be asynchronised in a subset of patients with LV or biventricular pacing, which may worsen coordination. The clinical significance of these findings remains to be defined.

Aged↗
PubMed2001

Beta(2) adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium.

OBJECTIVE: To define the effects of beta(2) adrenergic receptor stimulation on ventricular repolarisation in vivo. DESIGN: Prospective study. SETTING: Tertiary referral centre. PATIENTS: 85 patients with coronary artery disease and 22 normal controls. INTERVENTIONS: Intravenous and intracoronary salbutamol (a beta(2) adrenergic receptor selective agonist; 10-30 microg/min and 1-10 microg/min), and intravenous isoprenaline (a mixed beta(1)/beta(2) adrenergic receptor agonist; 1-5 microg/min), infused during fixed atrial pacing. MAIN OUTCOME MEASURES: QT intervals, QT dispersion, monophasic action potential duration. RESULTS: In patients with coronary artery disease, salbutamol decreased QT(onset) and QT(peak) but increased QT(end) duration; QT(onset)-QT(peak) and QT(peak)-QT(end) intervals increased, resulting in T wave prolongation (mean (SEM): 201 (2) ms to 233 (2) ms; p < 0.01). There was a large increase in dispersion of QT(onset), QT(peak), and QT(end) which was more pronounced in patients with coronary artery disease-for example, QT(end) dispersion: 50 (2) ms baseline v 98 (4) ms salbutamol (controls), and 70 (1) ms baseline v 108 (3) ms salbutamol (coronary artery disease); p < 0.001. Similar responses were obtained with isoprenaline. Monophasic action potential duration at 90% repolarisation shortened during intracoronary infusion of salbutamol, from 278 (4.1) ms to 257 (3.8) ms (p < 0.05). CONCLUSIONS: beta(2) adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium. The increase in dispersion of repolarisation provides a mechanism whereby catecholamines acting through this receptor subtype may trigger ventricular arrhythmias.

Action Potentials↗
PubMed2001

Symptomatic improvement after radiofrequency catheter ablation for typical atrial flutter.

OBJECTIVE: To assess the changes in quality of life, arrhythmia symptoms, and hospital resource utilisation following catheter ablation of typical atrial flutter. DESIGN: Patient questionnaire to compare the time interval following ablation with a similar time interval before ablation. SETTING: Tertiary referral centre. PATIENTS: 63 consecutive patients were studied. Four patients subsequently underwent an ablate and pace procedure, two died of co-morbid illnesses, and two were lost to follow up. The remaining 55 patients form the basis of the report. RESULTS: Patients were followed for a mean (SD) of 12 (9.5) months. Atrial flutter ablation resulted in an improvement in quality of life (3.8 v 2.5, p < 0.001) and reductions in symptom frequency score (2.0 v 3.5, p < 0.001) and symptom severity score (2.0 v 3.8, p < 0.001) compared with preablation values. There was a reduction in the number of patients visiting accident and emergency departments (11% v 53%, p < 0.001), requiring cardioversion (7% v 51%, p < 0.001), or being admitted to hospital for a rhythm problem (11% v 56%, p < 0.001). Subgroup analysis confirmed that patients with atrial flutter and concomitant atrial fibrillation before ablation and those with atrial flutter alone both derived significant benefit from atrial flutter ablation. Patients with concomitant atrial fibrillation had an improvement in quality of life (3.5 v 2.5, p < 0.001) and reductions in symptom frequency score (2.3 v 3.5, p < 0.001) and symptom severity score (2.2 v 3.7, p < 0.001) compared with preablation values. CONCLUSIONS: Ablation of atrial flutter is recommended both in patients with atrial flutter alone and in those with concomitant atrial fibrillation.

Adult↗
PubMed2001

Effects of intravenous dofetilide on induction of atrioventricular re-entrant tachycardia.

OBJECTIVE: To assess the efficacy and safety of intravenous dofetilide in preventing induction of atrioventricular re-entrant tachycardia. DESIGN: A multicentre, open, dose ranging trial. Fifty one patients with electrically inducible atrioventricular re-entrant tachycardia were allocated to one of five doses of dofetilide (1.5, 3, 6, 9, and 15 microgram/kg), two thirds of the dofetilide dose being given over a 15 minute loading period and the remainder over a 45 minute maintenance period. MAIN OUTCOME MEASURE: Responders were defined as patients in whom dofetilide prevented reinduction of atrioventricular re-entrant tachycardia at the end of the infusion. RESULTS: Intravenous dofetilide had no effect on tachycardia inducibility at the two lower doses (1.5 and 3 microgram/kg) but prevented the reinduction of tachycardia at the three higher doses (6, 9, and 15 microgram/kg) at a rate of 36% (11/31). There was a clear relation between plasma dofetilide concentrations and efficacy (p = 0.009). In non-responders, dofetilide increased the cycle length of induced atrioventricular re-entrant tachycardia. Dofetilide increased the atrial and ventricular effective refractory periods, as well as the antegrade and retrograde effective refractory period of the accessory pathway. Treatment related side effects were reported in four patients, one with a new sustained incessant supraventricular tachycardia. CONCLUSIONS: Dofetilide shows promise as an agent for the prevention of atrioventricular re-entrant tachycardia in patients without structural heart disease.

Adolescent↗
PubMed1999

Circadian variation of malignant ventricular arrhythmias in patients with ischemic and nonischemic heart disease after cardioverter defibrillator implantation. European 7219 Jewel Investigators.

OBJECTIVES: The purpose of this study was to examine the circadian variation of ventricular arrhythmias detected by an implantable cardioverter defibrillator in patients with and without ischemic heart disease. BACKGROUND: Previous studies have shown a circadian variation of ventricular arrhythmias, sudden death and myocardial infarction with a peak occurrence in the morning hours. The circadian pattern, which is similar for both arrhythmic and ischemic events, suggests that ischemia may play a critical role in the genesis of ventricular arrhythmias and sudden death. We hypothesized that, if ischemia plays an important role in the triggering of ventricular arrhythmias, the circadian pattern should be different in patients with ischemic heart disease compared with patients with nonischemic heart disease. METHODS: The circadian variation of ventricular arrhythmias recorded by an implantable cardioverter defibrillator was studied in 310 patients during a mean follow-up of 181 +/- 163 days. Two hundred four patients had a history of ischemic heart disease and 106 patients had nonischemic heart disease. The times of the episodes of ventricular arrhythmias were retrieved from the data log of each device during follow-up, and the circadian pattern was compared between the two groups. RESULTS: During follow-up, 1,061 episodes of ventricular arrhythmias were recorded by the device in the 310 patients. Six hundred eighty-two episodes occurred in the group of patients with ischemic heart disease and 379 occurred in the nonischemic heart disease group. The circadian variation of the episodes showed a typical pattern with a morning and afternoon peak in both groups of patients with ischemic and nonischemic heart disease, but there was no significant difference between the two groups. CONCLUSIONS: The circadian rhythm of ventricular arrhythmias in patients with ischemic heart disease is similar to patients with nonischemic heart disease, suggesting that the trigger mechanisms of the initiation of ventricular tachyarrhythmias may be similar, irrespective of the underlying heart disease.

Arrhythmias, Cardiac↗
PubMed1999

Survival after cardiac arrest or sustained ventricular tachycardia in patients with hypertrophic cardiomyopathy.

OBJECTIVES: The aim of this study was to evaluate the survival of patients with hypertrophic cardiomyopathy (HCM) after resuscitated ventricular fibrillation or syncopal sustained ventricular tachycardia (VT/VF) when treated with low dose amiodarone or implantable cardioverter defibrillators (ICDs). BACKGROUND: Prospective data on clinical outcome in patients with HCM who survive a cardiac arrest are limited, but studies conducted before the widespread use of amiodarone and/or ICD therapy suggest that over a third die within seven years from sudden cardiac death or progressive heart failure. METHODS: Sixteen HCM patients with a history of VT/VF (nine male, age at VT/VF 19 +/- 8 years [range 10 to 36]) were studied. Syncopal sustained ventricular tachycardia/ventricular fibrillation occurred during or immediately after exertion in eight patients and was the initial presentation in eight. One patient had disabling neurologic deficit after VT/VF. Before VT/VF, two patients had angina, four had syncope and six had a family history of premature sudden cardiac death. After VT/VF all patients were in New York Heart Association class I or II, three had nonsustained VT during ambulatory electrocardiography and 11 had an abnormal exercise blood pressure response. After VT/VF eight patients were treated with low dose amiodarone and six received an ICD. Prophylactic therapy was declined by two patients. RESULTS: Mean follow-up was 6.1 +/- 4.0 years (range 0.5 to 14.5). Cumulative survival (death or ICD discharge) for the entire cohort was 59% at five years (95% confidence interval: 33% to 84%). Thirteen (81%) patients were alive at last follow-up. Two patients died suddenly while taking low dose amiodarone, and one died due to neurologic complications of his initial cardiac arrest. Three patients had one or more appropriate ICD discharges during follow-up; the times to first shock after ICD implantation were 23, 197 and 1,124 days. CONCLUSIONS: This study shows that patients with HCM who survive an episode of VT/VF remain at risk for a recurrent event. Implantable cardioverter defibrillator therapy appears to offer the best potential benefit regarding outcome.

Adolescent↗
PubMed1998

Entrapment of an ablation catheter in the cardiac venous system: a case report.

Cannulation of the coronary sinus is a common procedure with infrequent complications. We report an unusual case of a steerable "dumb-bell" catheter passed through the ostium of the coronary sinus prior to an intended radiofrequency ablation procedure becoming stuck and requiring general anesthesia for extraction. We caution against the use of such catheters with a "waist" for the cannulation of the coronary sinus.

Adult↗
PubMed1998

Myocardial injury induced by radiofrequency and low energy ablation: a quantitative study of CK isoforms, CK-MB, and troponin-T concentrations.

We conducted a prospective, controlled study to investigate the use of CK-MB concentration and newer methods such as troponin-T concentration and CK isoforms, in the assessment of myocardial damage caused by radiofrequency current or low energy DC catheter ablation. The study population consisted of 3 consecutive patients who underwent low energy catheter ablation, 28 consecutive patients subjected to radiofrequency ablation, and 4 patients who were subjected to radiofrequency energy ablation but also had external DC shocks for cardioversion of atrial fibrillation that occurred during the procedure. The control group comprised eight subjects undergoing electrophysiological study. Prior to ablation and at 30 minutes, 1, 2, 6, and 12 hours following the procedure, serial blood samples were taken for measurement of troponin-T and CK-MB concentrations, and calculation of the MM3/MM1 and MB2/MB1 ratios. Troponin-T concentration was raised above normal in all patients subjected to low energy ablation and in all but two patients subjected to radiofrequency ablation. Only 42% of all patients subjected to ablation had at least one raised CK-MB concentration postablation. The MB2/MB1 ratio was raised in all but had at least one raised CK-MB concentration postablation. The MB2/MB1 ratio was raised in all but two patients following radiofrequency or low energy ablation but it was also abnormal in the preablation samples in nine patients. The MM3/MM1 ratio failed to detect myocardial damage in 71% of all patients. There was a statistically significant difference between the control and patient groups regarding all four indices of myocardial damage. Low energy ablation caused a significantly higher degree of myocardial damage compared with radiofrequency (RF); this effect could not be attributed to different numbers of total energy discharges. Our results indicate that catheter ablation, regardless of the mode of energy used, inflicts detectable injury upon the myocardium. This injury can be quantitated by using newer analytical techniques, such as serial, postablation measurements of troponin-T concentration.

Adult↗
PubMed1997

Use of troponin-T concentration and kinase isoforms for quantitation of myocardial injury induced by radiofrequency catheter ablation.

BACKGROUND: Although there remains particular concern about late malignant ventricular arrhythmias arising from myocardial damage induced by catheter ablation, the extent of myocardial injury resulting from clinical ablation procedures has not been fully studied. We conducted a prospective, controlled study to investigate the use of two newer markers of myocardial integrity, troponin-T concentration and creatine kinase isoforms, and a traditional marker, creatine kinase-MB concentration, in the assessment of myocardial injury following radiofrequency catheter ablation. METHODS AND RESULTS: The study population consisted of 28 consecutive patients subjected to radiofrequency catheter ablation, and the control group comprised eight subjects undergoing diagnostic electrophysiology study. Prior to ablation and at 30 min, 1, 2, 6, and 12 h following the procedure, blood samples were taken to measure troponin-T and creatine kinase-MB concentrations, and the separation of creatine kinase isoforms (MM3/MM1 and MB2/MB1 ratios). The troponin-T concentration was above normal in all but two patients following radiofrequency ablation, and the MB2/MB1 ratio was raised in all but one patient following ablation, but was also abnormal in the pre-ablation samples in seven patients. The MM3/MM1 ratio failed to detect myocardial injury in 75% of patients. Of patients subjected to ablation, in only 36% was the creatine kinase-MB concentration raised at least once post-ablation. Thirty minutes post-ablation, there was a statistically significant difference between the control and patient groups only as regards troponin-T concentration. There was a significant association between troponin-T concentration immediately post-procedure, the number of discharges delivered (r = 0.52, P = 0.006) and maximum power used (r = 0.48, P = 0.009). CONCLUSION: Our results indicate that catheter ablation inflicts a cumulative, detectable injury upon the myocardium. This injury can be quantitated by using newer analytical techniques, such as serial, post-ablation measurements of troponin-T concentration.

Adult↗
PubMed1997

Performance of basic ventricular tachycardia detection algorithms in implantable cardioverter defibrillators: implications for device programming.

Around 20% of patients with third generation implantable cardioverter defibrillators receive inappropriate therapy, usually triggered by atrial fibrillation. This is because the criteria used for ventricular tachycardia detection by current implantable cardioverter defibrillators are based on the analysis of a sequence of RR intervals and may be inappropriately satisfied by supraventricular tachyarrhythmias. Algorithms for ventricular tachycardia detection were challenged against the full RR interval sequences from 482 spontaneous episodes of atrial fibrillation and 260 spontaneous episodes of ventricular tachycardia to determine their ability to discriminate between the arrhythmias. The sensitivities and specificities of the algorithms were calculated over a wide range of programmable parameters. For a given window length and detection interval, the most stringent algorithms, that required all beats to be classified as "fast", were more specific than those allowing a proportion of "normal" intervals, even after adjustment for differing sensitivity. These differences were less marked for faster tachycardias. Specificity increased with the detection window length to a limit of approximately 18 beats. We conclude that ventricular tachycardia is detected with the highest specificity if all beats in an analyzed sequence are required to be "fast," even after lengthening of the tachycardia detection interval to maintain sensitivity. Further improvement in algorithm performance may require the incorporation of criteria such as tachycardia onset and stability.

Algorithms↗
PubMed1997

Electrophysiological effects of E 4031, a drug with selective class III properties, in man.

We studied the electrophysiological effects of E 4031, given in a dose ascending manner (1.5, 3.0, and 6.0 micrograms/kg over 5 min followed by 0.1, 0.2, and 0.4 microgram/kg per min for 60 min, respectively) to 19 volunteers. There were significant, dose related linear increase in QT and QTc intervals, in atrial functional and effective refractory periods (ERPs) at a paced cycle length of 400 ms, and in ventricular functional and ERPs at a paced cycle length of 600 ms. There was no significant change in the AH and HV intervals or QRS duration. No significant proarrhythmic or other side effects were encountered during the administration of the drug. E 4031 prolongs atrial and ventricular refractoriness without significantly affecting AV or intraventricular conduction, consistent with selective Class III properties. At the doses used in the present study, intravenous infusion of E 4031 appears to be safe and well tolerated.

Adolescent↗
PubMed1997

Radiofrequency catheter ablation of accessory atrioventricular pathways: primary failure and recurrence of conduction.

OBJECTIVE: To identify possible factors associated with primary failure of radiofrequency ablation of accessory pathways or recurrence of accessory pathway conduction. PATIENTS AND METHODS: Radiofrequency ablation of accessory pathways failed in 25 of 243 patients, and recurrence of accessory pathway conduction occurred in an additional 13 patients. Factors possibly related to primary failure and recurrence were analysed. RESULTS: Primary failure and recurrence were less frequent in patients with left sided pathways (7% v 19%; 4% v 24%; P = 0.04). The factors that might relate to primary failure included an unstable catheter position (seven patients), a possible epicardial pathway (six patients), or misdiagnosis of accessory pathway location (two patients). The major factors for recurrence included the stability of the local atrial electrogram < or = 0.5 together with the stability of the local ventricular electrogram < or = 0.8, and prolonged time to pathway conduction block > or = 12 seconds). Thirty one patients underwent repeat ablation which was successful in 28. CONCLUSIONS: Primary failure and recurrence were more frequent in patients with right sided pathways. An unstable catheter position and a possible epicardial pathway location are the main contributing factors for primary failure, while unstable local electrograms and prolonged time to block are independent predictors for recurrence.

Adolescent↗