Stephen S. Furniss

Errors in manual measurement of QT intervals.

OBJECTIVE--To quantify the errors associated with manual measurement of QT intervals and to determine the source of the errors. DESIGN--A randomised study of QT measurement by four cardiologists of electrocardiograms plotted on paper in presentations with different noise levels, paper speeds, amplifier gains, and with and without a second QRST complex to indicate the RR interval. SUBJECTS--Four electrocardiograph leads (I, aVR, V1, V5) recorded in eight healthy people relaxing in a semirecumbent position. MAIN OUTCOME MEASURES--Manual measurement of QT interval in 512 electrocardiograms (eight subjects x four leads x eight presentations x two repeats) by each of four cardiologists. RESULTS--QT intervals measured were significantly longer with greater amplifier gain: by 8 ms for a doubling of gain (p < 0.005), equivalent to a doubling of T wave height. QT intervals measured were significantly longer at slower paper speeds: by 11 ms when paper speed was reduced from 100 to 50 mm/s (p < 0.001) and by 16 ms when speed was further reduced from 50 to 25 mm/s (p < 0.001). Neither the presence of noise nor the presence of a second QRST complex altered the mean QT measurements. There were consistent differences in the measurements between cardiologists, amounting to a maximum mean difference of 20 ms. CONCLUSIONS--Manual measurement of QT interval is significantly affected by the paper speed used to plot the electrocardiogram and by electrocardiogram gain, and hence also T wave amplitude. Manual QT measurement also differed consistently with different cardiologists.

Clinical and electrophysiological differences between patients with arrhythmogenic right ventricular dysplasia and right ventricular outflow tract tachycardia

AIMS Radiofrequency catheter ablation is considered first line treatment for symptomatic patients with right ventricular outflow tract tachycardia (RVOT). The role of ablation in arrhythmogenic right ventricular dysplasia (ARVD) is more limited. As such, differentiating between the two conditions is essential. METHODS AND RESULTS This study compared non-invasive findings, magnetic resonance images (MRI), invasive electrophysiological characteristics, results of ablation and long-term outcome in 50 consecutive patients with RVOT (33) or ARVD (17). Structural abnormalities were uniform in the ARVD group; in addition 18 (54%) of the RVOT tachycardia group had MRI abnormalities. At electrophysiological study the tachycardia in the ARVD group displayed features of re-entry in over 80%, but behaved with a triggered automatic basis in 97% with RVOT. Ablation was complete or partial success in 12 (71%) patients with ARVD and ventricular tachycardia (VT) recurred in eight (48%). In the RVOT patients, ablation was a complete success in 97% with recurrent VT in 6%. Long-term success in the RVOT patients was 95% in both patients with and without MRI abnormalities. CONCLUSIONS Electrophysiological characterization can differentiate ARVD from RVOT. The finding of abnormalities on MRI does not have any bearing on arrhythmia mechanism, acute or long-term success of RFA.

Reduction in ST segment elevation after thrombolysis predicts either coronary reperfusion or preservation of left ventricular function.

The usefulness of a reduction in ST segment elevation to predict coronary reperfusion in myocardial infarction remains uncertain. ST segment changes and angiographic findings were compared in 45 patients soon after thrombolysis. The percentage ST segment change 3 hours after treatment (in the lead showing the greatest initial ST elevation) was compared with the TIMI perfusion grade (thrombolysis in myocardial infarction trial) obtained between 90 minutes and 3 hours after treatment. Global ejection fraction and regional wall motion were assessed by cineventriculography (11 (5) days (mean (SD))) and by gated blood pool imaging (44 (11) days). Prediction of coronary patency by a reduction of greater than 25% in ST segment elevation 3 hours after thrombolytic treatment had a sensitivity of 97% but a specificity of only 43%. Where the ST segment elevation was reduced by greater than 25% the global ejection fraction was well maintained whether or not the infarct vessel was patent. In patients with a reduction of less than 25% in ST elevation, the ejection fraction was significantly lower and regional wall motion abnormality more severe. Reduction in ST elevation of greater than 25% within 3 hours of thrombolysis indicates either a patent infarct artery or preservation of left ventricular function. When the ST segment elevation does not fall by greater than 25% persistent coronary occlusion is likely (predictive accuracy 86%) and is associated with a lower ejection fraction. These patients may benefit from further treatment or additional interventions.

Pulmonary vein ablation for idiopathic atrial fibrillation: six month outcome of first procedure in 100 consecutive patients

Objectives: To report six month outcome in patients undergoing their first pulmonary vein ablation procedure for idiopathic atrial fibrillation (AF) at a “non-pioneering” hospital. Design: Prospective observational study. Setting: Specialist electrophysiology unit at a university hospital. Patients: The first 100 consecutive patients undergoing their first pulmonary vein catheter ablation procedure for highly symptomatic, drug resistant AF in the period 1999–2002. Main outcome measures: Incidence of symptomatic or asymptomatic, Holter documented AF six months after ablation. Results: Mean patient age was 52 years (range 23–73 years), mean length of AF history 53 months (range 6–180 months), mean number of antiarrhythmic drug failures was 3 (range 1–5), and 81 were men. At the time of the ablation procedure, 64 had progressed to persistent AF and 23 had increased transverse left atrial diameter. The number of pulmonary veins ablated in each patient was one in 11, two in 45, three in 36, and four in 8. Six months after ablation, 55 patients were consistently in sinus rhythm, asymptomatic, and without any Holter evidence of AF. The chance of being in sinus rhythm was 73% (29 of 64) in those with paroxysmal as compared with only 45% (26 of 36) in those with persistent AF at the time of ablation (p  =  0.01). Outcome was not influenced by patient age, length of AF history, or duration of persistent AF before ablation or to left atrial dimension. Follow up was complete and no patient has died or experienced a stroke during or after ablation; nor have any developed symptoms of late pulmonary vein stenosis. However, other complications occurred during or shortly after the procedure in 12 patients, including cardiac tamponade in six. Conclusions: In selected patients with drug resistant AF, focal pulmonary vein catheter ablation offers a realistic prospect of achieving stable sinus rhythm compared with alternatives. However, it is a complex form of ablation with a significant risk of serious complications. Although a new milestone in arrhythmia management, the optimum ablation technique is still evolving and any impact on the natural history of AF remains to be determined.

Surface atrial frequency analysis in patients with atrial fibrillation: Assessing the effects of linear left atrial ablation

Introduction: Our group has shown previously that measurements of atrial frequency can be obtained from surface 12‐lead ECG recordings of patients during atrial fibrillation (AF), using a combination of principal component and Fourier transform algorithms. Such measurements are reproducible over time and change with drug manipulation of the arrhythmia.

Surgery for ventricular tachycardia associated with right ventricular dysplasia: disarticulation of right ventricle in 9 of 10 cases.

Ten patients (nine men, one woman; mean age 39 years) with arrhythmogenic right ventricular dysplasia underwent surgery to control life-threatening drug refractory ventricular arrhythmias. All had ventricular tachycardia causing syncope and six had a history of cardiac arrest. In all a minimum of three antiarrhythmic drugs (mean five) had been ineffective. At operation, the right ventricle was grossly diseased in all patients. Ventricular tachycardias were induced and mapped intraoperatively in all patients. The surgical plan was to ablate the arrhythmogenic focus if it was less than 4 cm2; one patient was so managed. Of the remaining nine, four underwent partial (approximately 40% of the right ventricular free wall) and five underwent total right ventricular disarticulation. All survived the operation and are alive at a mean follow-up interval of 24 months (range 5 to 67). Two patients developed new sustained ventricular tachycardias. These were well tolerated and, unlike the original arrhythmias, were easily controlled by drug treatment. All patients who underwent right ventricular disarticulation manifested signs of right heart failure in the early postoperative period, but these lessened progressively with the development of systolic septal movement into the right ventricular cavity. All 10 patients are in New York Heart Association class I or II at last review. In selected patients with arrhythmogenic right ventricular dysplasia, surgery offers a curative treatment for ventricular tachycardia and should be considered for patients whose arrhythmias are life-threatening and refractory to drug treatment.

Systolic coronary occlusion due to myocardial bridging — a rare cause of ischaemia

Myocardial bridging causing systolic occlusion of the left anterior descending coronary artery was identified in a 47-year-old man with angina. A fixed anterolateral wall defect was demonstrated on thallium imaging and he underwent successful division of the bridge resulting in abolition of his symptoms and disappearance of the thallium defect.

Surgery for postinfarction ventricular tachycardia in the pre-implantable cardioverter defibrillator era : early and long term outcomes in 100 consecutive patients

OBJECTIVE To report outcome following surgery for postinfarction ventricular tachycardia undertaken in patients before the use of implantable defibrillators. DESIGN A retrospective review, with uniform patient selection criteria and surgical and mapping strategy throughout. Complete follow up. Long term death notification by OPCS (Office of Population Censuses and Statistics) registration. SETTING Tertiary referral centre for arrhythmia management. PATIENTS 100 consecutive postinfarction patients who underwent map guided endocardial resection at this hospital in the period 1981–91 for drug refractory ventricular tachyarrhythmias. RESULTS Emergency surgery was required for intractable arrhythmias in 28 patients, and 32 had surgery within eight weeks of infarction (“early”). Surgery comprised endocardial resections in all, aneurysmectomy in 57, cryoablations in 26, and antiarrhythmic ventriculotomies in 11. Twenty five patients died < 30 days after surgery, 21 of cardiac failure. This high mortality reflects the type of patients included in the series. Only 12 received antiarrhythmic drugs after surgery. Perioperative mortality was related to preoperative left ventricular function and the context of surgery. Mortality rates for elective surgery more than eight weeks after infarction, early surgery, emergency surgery, and early emergency surgery were 18%, 31%, 46%, and 50%, respectively. Actuarial survival rates at one, three, five, and 10 years after surgery were 66%, 62%, 57%, and 35%. CONCLUSIONS Surgery offers arrhythmia abolition at a risk proportional to the patient’s preoperative risk of death from ventricular arrhythmias. The long term follow up results suggest a continuing role for surgery in selected patients even in the era of catheter ablation and implantable defibrillators.

Practical considerations in the use of sotalol for ventricular tachycardia and ventricular fibrillation

Sotalol is a unique antiarrhythmic drug that combines beta-blocking effects with actions to prolong action potential duration. The net effect is a drug that is efficacious in the management of ventricular tachyarrhythmias. Although sotalol has effects on both heart rate and QT interval, these effects do not help predict the antiarrhythmic efficacy of the agent. Changes in QT dispersion may, however, prove to be relevant to both the antiarrhythmic effects and the arrhythmogenic effects of sotalol. Thus, although sotalol may occasionally cause torsades de pointes, this complication may be predictable and clinically controllable. Sotalol is well tolerated, and it may be used, with caution, in some patients with impaired myocardial contractile performance, despite its beta-blocking action. Sotalol has an important indication for the management of ventricular tachyarrhythmias.

Electrocardiographic Features of Septal Location of Right Ventricular Outflow Tract Tachycardia

A consistent 12-lead electrocardiogram (ECG) morphology and characteristic frontal plane axis shift from sinus rhythm to ventricular tachycardia (VT) was demonstrated in 10 consecutive patients with idiopathic right ventricular outflow tract (RVOT) VT. All arrhythmias were successfully ablated on the septal side of the RVOT.