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G T Evans

Publications and source records attributed to G T Evans.

At least 19 recordsLinked to original sources
PubMed1994

Evaluation of electrocardiographic criteria for right atrial enlargement by quantitative two-dimensional echocardiography.

OBJECTIVES: This study was conducted to evaluate the sensitivity and specificity of traditional electrocardiographic (ECG) criteria for right atrial enlargement and identify improve criteria, using quantitative two-dimensional echocardiography. BACKGROUND: Traditional ECG criteria for right atrial enlargement, such as P pulmonale, have been increasingly criticized as insensitive and nonspecific. Quantitative two-dimensional echo-cardiography has been shown to be a useful method for evaluating atrial size. METHODS: Hospitalized patients with mild, moderate and severe right atrial enlargement were selected from our laboratory's data base and compared with age- and gender-correlated hospitalized control subjects. After exclusions, 100 patients with right atrial enlargement and 25 control patients remained. Planimetric measurement of right atrial volumes was accomplished by two independent observers using the single-plane method of discs algorithm. Electrocardiograms were independently evaluated for current and newly proposed right atrial enlargement criteria. RESULTS: Fifty-two patients (52%) were in sinus rhythm, 41 were in atrial fibrillation, 5 were in atrial flutter, and 2 were in ectopic atrial rhythm. All control subjects were in sinus rhythm. The right atrial volume for the control group was 35.0 +/- 7.4 ml (mean +/- SD), with a narrow, roughly normal distribution. The right atrial volume for the patient group was 147.6 +/- 69.1 ml (median 127.2) in a wide, skewed distribution. The difference of mean values was highly significant (p = 0.0001). Right ventricular enlargement was found to some degree in all patients with right atrial enlargement. The most powerful predictors of right atrial enlargement were a QRS axis > 90 degrees, a P wave height in lead V2 > 1.5 mm and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. P pulmonale detected only 6% of patients with right atrial enlargement. CONCLUSIONS: Using quantitative two-dimensional echocardiography, we found that most previously reported ECG criteria for right atrial enlargement have low predictive power. The best predictors of right atrial enlargement were a P wave height > 1.5 mm in lead V2 and, as new criteria, a QRS axis > 90 degrees and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. Further studies are needed to prospectively validate these findings.

Atrial Function, Right↗
PubMed1993

Left ventricular function immediately after intravenous cocaine: a quantitative two-dimensional echocardiographic study.

OBJECTIVES: We tested the hypothesis that intravenous cocaine, in doses commonly self-administered in nonmedical settings, causes acute myocardial ischemia and left ventricular dysfunction. BACKGROUND: Cocaine-induced cardiac complications are responsible for a growing number of deaths in young people, but the mechanism by which cocaine induces these complications is unclear. METHODS: We performed 12-lead electrocardiography and quantitative two-dimensional echocardiography in 20 subjects before and after single intravenous doses of high dose cocaine (1.2 mg/kg body weight), low dose cocaine (0.6 mg/kg) and placebo. RESULTS: At 2 to 7 min after cocaine administration, the rate-pressure product was increased significantly from baseline (high dose 73%, low dose 63%, placebo 8%, p < 0.001 for either dose vs. placebo). During this time, electrocardiography demonstrated dose-related nonspecific changes (high dose in 14 of 20 subjects, low dose in 9 of 20 subjects, placebo in 2 of 20 subjects, p < 0.002 for either dose vs. placebo). In contrast, echocardiography showed that the frequency of hyperdynamic left ventricular wall segments doubled after high dose cocaine compared with placebo (34% [108 of 318] vs. 16% [51 of 319], respectively, p = 0.0001) but that there was no change in either left ventricular ejection fraction (high dose 66 +/- 9%, placebo 67 +/- 6%, p = NS) or wall motion score index (high dose 0.67 +/- 0.44, placebo 0.85 +/- 0.30, p = NS). CONCLUSIONS: We conclude that intravenous cocaine, in doses commonly self-administered in nonmedical settings, does not cause acute myocardial ischemia or left ventricular dysfunction. We speculate that cocaine-induced cardiac complications are caused by idiosyncratic coronary artery vasospasm, by exceptionally high dosages or by cocaine-induced coronary artery thrombosis.

Adult↗
PubMed1992

Comparison of a vectorcardiographically derived 12-lead electrocardiogram with the conventional electrocardiogram during wide QRS complex tachycardia, and its potential application for continuous bedside monitoring.

Previous investigators published conflicting reports comparing a vectorcardiographically derived electrocardiogram (ECGD) with the conventional 12-lead one (ECG). Prior comparisons were obtained in adults during sinus rhythm, but never in patients with wide QRS complex tachycardia. The ECGD was evaluated during baseline rhythms in patients with varying cardiac diagnoses, and the diagnostic accuracy of the 2 methods was compared during 64 episodes of wide QRS complex tachycardia in 49 patients during cardiac electrophysiologic study. All leads of the 12-lead ECGD closely resembled the conventional ECG in baseline and tachycardia tracings, except leads V3 and V4. QRS voltages were less in the ECGD, resulting in an inability to detect left ventricular hypertrophy in one third of patients with that diagnosis. There was excellent agreement between the ECGD and ECG in diagnosing prior myocardial infarction (92%), ventricular preexcitation patterns (100%), bundle branch and fascicular blocks (100%), and axis deviation. The ECGD was equally as valuable as the ECG in the diagnosis of wide QRS complex tachycardia. There was perfect agreement between the 2 lead systems in application of the morphologic criteria differentiating supraventricular tachycardia with aberration from ventricular tachycardia in leads V1, V2 and V6, and for criteria requiring axis determination and measurement of RS intervals in the precordial leads. The ECGD tracings contained less muscle artifact during body movements (e.g., after direct-current defibrillation). In conclusion, the ECGD's close correlation with the ECG, and its technical superiority and simple 5 torso-positioned electrode configuration make it worth pursuing as an option for continuous bedside monitoring.

Adult↗
PubMed1991

Predictors of in-hospital mortality after DC catheter ablation of atrioventricular junction. Results of a prospective, international, multicenter study.

BACKGROUND: The Catheter Ablation Registry was the first international, multicenter, prospective study of the safety and efficacy of catheter ablation. METHODS AND RESULTS: From August 1987 through March 1990, the study comprised 136 patients in whom only DC energy was used in attempted production of third-degree atrioventricular block to treat uncontrollable supraventricular tachycardias. Eight patients died during hospitalization for ablation. In seven (5.1%), the ablation may have contributed to their deaths. Causes of death included ventricular fibrillation (five patients, three with polymorphic ventricular tachycardia), progressive heart failure (one patient), and respiratory failure (two patients, one dying after resuscitation from ventricular fibrillation). Compared with survivors, patients who died were more likely to have had prior aborted sudden death (38% versus 2%, p less than 0.05), congestive heart failure (88% versus 22%, p less than 0.001), cardiomyopathy (50% versus 16%, p less than 0.05), lower baseline systolic blood pressure (106 versus 138 mm Hg, p less than 0.001), prolonged baseline and postablation corrected QT interval (p less than 0.01), and markedly reduced ejection fraction (27% versus 52%, p less than 0.001). Ablation successfully produced third-degree atrioventricular block in 88% of the patients who died and in 83% of survivors. CONCLUSIONS: Catheter ablation of the atrioventricular junction with DC energy carries a significant, previously unrecognized risk of death (5.1%), particularly from lethal arrhythmias, when applied to patients with severe left ventricular dysfunction. Great care should be taken in these seriously ill patients to guard against postablation ventricular arrhythmias.

Bundle of His↗
PubMed1986

Catheter ablation for control of ventricular tachycardia: a report of the percutaneous cardiac mapping and ablation registry.

Catheter ablation of ventricular tachycardia is a procedure of last resort in critically ill patients. The Percutaneous Cardiac Mapping and Ablation Registry was able to collect data on 88 patients undergoing ablation of ventricular tachycardia foci. The mean following interval for the group was 10 +/- 8 months. Results were divided into three categories: Group I patients remained asymptomatic and were on no antiarrhythmic medications (33%); Group II remained asymptomatic and took antiarrhythmic agents (38%); Group III patients were considered unsuccessful and consisted of 29 percent of the total. More than one-third of patients received two shocks; the remainder received from one to five shocks. Overall mortality included four procedure-related deaths and total follow-up mortality was 25 percent. Catheter ablation for ventricular tachycardia should be undertaken only in highly specialized centers with an expert and experienced electrophysiologist with immediate surgical back-up available.

Adolescent↗
PubMed1979

Electrophysiologic effects of disopyramide phosphate on sinus node function in patients with sinus node dysfunction.

The electrophysiologic effects of intravenously administered disopyramide (2 mg/kg) on three parameters of sinus node function were examined in 16 symptomatic patients with sinus node dysfunction. Based on their ECG data before study, patients were subdivided into group A (n = 8), those with sinus pauses and/or sinoatrial (SA) exit block; and group B (n = 8), those with sinus bradycardia. Disopyramide shortened spontaneous cycle length in 10 of 16 patients and lengthened it in six--markedly so (91%) in one patient. Estimated SA conduction time decreased in seven of 14 patients and increased in seven. Two patients developed second degree SA exit block after disopyramide. Maximum sinus node recovery time was prolonged by disopyramide in 11 of 16 patients and markedly so in four. For the group as a whole there was no significant difference in spontaneous cycle length, maximum sinus node recovery time or estimated SA conduction time. P-wave and QRS durations and H-V intervals were significantly lengthened by disopyramide. Marked depression of the three parameters of sinus node function occurred in three group A patients and in one group B patient who had persistent severe sinus bradycardia. These four patients also had secondary pauses after termination of rapid atrial pacing under control conditions. Disopyramide should be administered cautiously to patients with sinus node dysfunction, particularly those with sinus pauses, SA exit block or secondary pauses.

Adult↗
PubMed1978

Electrophysiologic testing in patients with sinus pauses and/or sinoatrial exit block.

28 symptomatic patients with documented episodes of sinus pauses and/or sinoatrial exit block underwent electrophysiologic study. Abnormal responses to electrophysiologic testing were observed in 23/28 patients (82%). Abnormal prolongation of the maximum sinus node recovery time (SNRT max) occurred in 17/28 (61%) patients, of postpacing cycles 2.10 (secondary pauses) occurred in 21/28 (75%), and of estimated sinoatrial conduction time occured in 15/28 (54%). The incidence of abnormal responses to rapid atrial pacing (prolonged SNRT max or secondary pauses) (22/28, 79%) was higher than the incidence of abnormal responses to premature atrial stimulation (15/28, 54%) (P less than 0.005). Life-threatening cardiac arrhythmias were observed, prior to electrophysiologic study, in 5 out of 28 (18%) patients. Symptomatic patients with sinus pauses and/or sinoatrial exit block frequently (23/28, 82%) showed abnormal responses to electrophysiologic testing and have a relatively high incidence of life-threatening arrhythmias.

Adult↗
PubMed1977

Prospective study of angiotensin II response to positional change in pregnancy-induced hypertension.

The response of endogenous angiotensin II levels to positional change, lateral to supine recumbency, was investigated in a prospective study of 55 primigravid patients during the last half of pregnancy. Blood samples were obtained in the lateral and supine recumbent positions. The mean supine angiotensin II level was significantly higher between 29 and 34 weeks' gestation in those patients destined to develop pregnancy-induced hypertension than in those who remained normotensive (P less than 0.05). As gestation advanced, the mean per cent relative change of angiotensin II from the lateral to the supine position altered from negative to positive in those patients destined to develop pregnancy-induced hypertension, whereas it remained negative in those patients who remained normotensive. These findings are discussed in relation to pathophysiologic alterations in the development of pregnancy-induced hypertension.

Angiotensin II↗
PubMed1977

Traumatic acute pericardial tamponade.

Pericardial tamponade should always be suspected in the clinical setting of any penetrating wound to the thorax or upper abdomen. The most reliable diagnostic criterion is the triad of hypotension, tachycardia and an elevated central venous pressure. Pericardiocentesis should be performed as a temporizing measure until definitive surgical therapy can be carried out. If the patient suddenly decompensates or arrests in the emergency department, immediate thoractomy with evacuation of the pericardial clot and open chest cardiac massage should be performed. Four case reports are presented. The pathophysiology and treatment are reviewed in detail.

Adult↗