Subspecialisation in cardiology care and outcome: should clinical services be redesigned, again?

BACKGROUND: Inpatient management of cardiac patients by cardiologists results in reduced mortality and hospitalisation. With increasing subspecialisation of the field because of growing management complexity and use of technological innovations, the impact of sub-specialisation on patient outcomes is unclear. AIM: To investigate whether management by subspecialty cardiologists impacts the outcomes of patients with subspecialty-specific diseases. METHODS: All patients admitted to a tertiary centre over nine years with a diagnosis of heart failure, acute coronary syndrome (ACS) or primary arrhythmia were reviewed. The outcomes of these patients managed by cardiologists subspecialised in their admission diagnosis (heart failure specialists, interventionalists and electrophysiologists) were compared with those treated by general cardiologists. RESULTS: Heart failure was diagnosed in 1704 patients, ACS in 7763 and arrhythmia in 4398. There was no difference in length of stay (LOS) (P = 0.26), mortality (P = 0.57) or cardiovascular readmissions (P = 0.50) in heart failure patients treated by general cardiologists compared with subspecialists. In ACS patients, subspecialty management was associated with reduced LOS, cardiovascular readmissions and mortality (all P < 0.05). This reduction in mortality was seen mainly in lower risk patients (P < 0.05). There was a reduction in LOS and cardiovascular readmissions in arrhythmia patients receiving subspecialty management (both P < 0.05) but no difference in mortality (P = 0.14). ACS patients managed by interventionalists were more likely to undergo coronary intervention (P < 0.05). Electrophysiologists more frequently referred patients for catheter ablation and pacemaker implantation than general cardiologists (P < 0.05). CONCLUSIONS: The benefits of subspecialty care seem attributable to the appropriate selection of patients who would benefit from technological innovations in care. These results suggest that the development of healthcare systems which align cardiovascular disease with the subspecialist may be more effective.

Left sided arrhythmogenic ventricular dysplasia in siblings.

A 32 year old man with no previous medical history suffered a sudden cardiac death. Post mortem examination revealed circumferential fibro-fatty infiltration of the left ventricular myocardium. Histological appearance was characteristic of arrhythmogenic right ventricular dysplasia but unusual for its localisation only to the left ventricle. As a result of this sudden cardiac death the family of the deceased was screened for cardiac disease. A brother of the index case was 36 years old and free of cardiac history and symptoms. Cardiac investigations revealed a functionally and electrically abnormal left ventricle with apparent sparing of the right ventricle. The brothers may have a left sided form of arrhythmogenic ventricular dysplasia and illustrate the importance of screening family members of young victims of sudden cardiac death.

Serum mucin antigen (CASA) as a marker of amiodarone-induced pulmonary toxicity.

Amiodarone is used to treat life-threatening cardiac arrhythmias. Amiodarone-induced pulmonary toxicity (APT) can be difficult to diagnose. APT may result in increased mucus production and mucin expression. Thus, serum mucin-1 was evaluated as a marker for amiodarone-induced pulmonary toxicity. Concentrations of mucin-1 in peripheral blood were determined using cancer-associated serum antigen (CASA) assay in patients taking amiodarone. Eight of ten patients who developed major amiodarone toxicity had high serum CASA levels. Patients with toxicity had a significantly higher mean rank CASA concentration compared with those without major toxicity. CASA shows potential as a marker for amiodarone-induced toxicity, particularly pulmonary toxicity.

Effects on cardiac performance of atrioventricular node catheter ablation using radiofrequency current for drug-refractory atrial arrhythmias.

Patients with atrial fibrillation or atrial flutter (AF) are candidates for radiofrequency (RF) catheter ablation of the atrioventricular (AV) node with the aim being to control heart rate. As patients with AF can have markedly impaired ventricular function, information concerning the hemodynamic effects of AV node ablation using RF current would be valuable. Fourteen consecutive patients (mean age 65 +/- 3 years) with drug-resistant AF underwent AV node catheter ablation with RF current and had permanent pacemaker implantation. The mean left ventricular ejection fraction (EF) by two-dimensional echocardiography immediately before ablation was 42 +/- 3% (range 14%-54%) and their mean exercise time was 4.4 +/- 0.4 minutes. Complete AV block was achieved in all 14 patients with 6 +/- 2 RF applications (range 1-18). There was no evidence of any acute cardiodepressant effect associated with delivery of RF current, and EF 3 days after ablation was 44 +/- 4%. By 6 weeks after ablation, the left ventricular EF was significantly improved compared to baseline (47 +/- 4% postablation vs 42 +/- 3% preablation; P < 0.05), and this modest increase in EF was accompanied by an improvement in exercise time (5.4 +/- 0.4 min). In conclusion, delivery of RF current for AV node catheter ablation in patients with AF and reduced ventricular function is not associated with any acute cardiodepressant effect. On the contrary, improved control of rapid heart rate following successful AV node ablation is associated with a modest and progressive improvement in cardiac performance.

Clinical implications of electrophysiology study findings in patients with chronic bifascicular block and syncope.

Electrophysiology study was performed in 93 patients with bifascicular block and unexplained syncope. Clinical evidence of organic heart disease was present in 33 (35%). Electrophysiological abnormalities were detected in 45 patients (48%). Of these, 36 had distal conduction disease, including 28 with an HV interval greater than 55 ms (mean 76.4 ms), and eight who developed infraHisian block following either intravenous procainamide (four) or atrial pacing (four). Sick sinus syndrome was evident in six patients and a further two had carotid sinus hypersensitivity. Sustained monomorphic ventricular tachycardia (VT) was induced in only three patients, two of whom also had prolonged HV interval. Among the 93 patients, 45 had therapy which was guided by positive findings at electrophysiology study (Group 1). Of these, 42 received permanent pacemakers, two were treated with combined permanent pacing and antiarrhythmic drug therapy, and one was treated with antiarrhythmic drug alone. In addition, eight patients without electrophysiologic abnormalities were treated empirically by pacing (Group 2). Finally, 40 patients without electrophysiologic abnormalities received no specific therapy (group 3). At a mean follow-up of 39 months (range two-125 months), recurrence of syncope had occurred in 4% of Group 1 patients, and 25% of Group 3 patients (p less than 0.05). No patient in Group 2 had had recurrence. Total mortality was 40%, including 47% of patients in Group 1, 25% of Group 2, and 35% of Group 3. Death was sudden in seven patients. We concluded that among patients with bifascicular block and syncope, therapy directed by findings at electrophysiology study was associated with symptomatic improvement, but mortality was not significantly influenced.(ABSTRACT TRUNCATED AT 250 WORDS)

Procainamide administration during electrophysiology study--utility as a provocative test for intermittent atrioventricular block.

The utility of procainamide, up to 10 mg/kg IV, as a provocative test for intermittent high degree atrioventricular (AV) block was evaluated in a total of 89 patients. Forty two patients had resting 1:1 AV conduction but had bifascicular block and a history of syncope. High degree AV block had not been documented in anyone. Before procainamide, the HV interval was greater than 60 ms in 17 of the 42 patients but no patient developed infra-Hisian block with fixed rate atrial pacing or following programmed atrial extrastimuli. Procainamide administration lengthened the mean HV interval by 11.9 ms and in seven (14%) the HV increment was marked, 15-75 ms. Furthermore, four (9.5%) of these 42 patients developed second or third degree infra-Hisian block and in two of these four patients, the HV prior to procainamide administration was normal or only mildly prolonged (less than 60 ms). The findings were compared to those in three "control" groups. Among four patients with bifascicular block, previously documented transient AV block but 1:1 AV conduction at the time of study, three developed high degree AV block following procainamide. Among five patients with bifascicular block but without syncope nor documented high degree AV block, the mean HV interval lengthened by 18.8 ms and in three the HV increment was 24-30 ms. In another 38 patients with neither syncope nor an intraventricular conduction defect, the mean HV interval lengthened by 5.3 ms and in two cases by 20-25 ms. Most importantly, high degree AV block was never observed in the latter two groups. During follow-up of up to 10 years (mean 46 months), three of the seven patients in whom procainamide provoked high degree AV block have subsequently progressed to fixed complete AV block. Although the incidence of provocation of AV block was relatively low, it was concluded that, among patients with possible intermittent AV block, administration of procainamide as a test of distal conduction has limited value but is still useful, and may provide information additional to that obtained from mere assessment of the HV interval.

Sinus node sequences after atrial stimulation: similarities of effects of different methods.

Sinoatrial conduction is commonly assessed from features of the initial cycle after a single atrial extrastimulus or eight beats atrial pacing. In contrast, sinus node automaticity is assessed by the duration of the first interval after prolonged atrial pacing. The return cycle and initial sequences after these different methods were compared in 10 subjects with normal sinus node function and 30 patients with sick sinus syndrome. Typically, sequences after all three methods showed a maximally prolonged first interval with a progressive decrease over five or more cycles. A model of recovery from overdrive suppression was used to compute the elements of conduction time and automaticity in the first interval. The sequences which followed a single extrastimulus and pacing were similar, the only index which increased significantly with prolonged pacing was associated with the degree of suppression of automaticity. The computed component of sinoatrial conduction in the return cycle was similar for all three methods. Thus all three conventional methods which consider only the initial post-stimulation interval measure both sinoatrial conduction and sinus node automaticity. The separate components of automaticity and conduction may be assessed by analysis of the total sequence.

Comparison of exponential and hyperbolic models of conduction through the atrioventricular node.

Conduction through the atrioventricular node (AVN) is assessed during electrophysiology study by relating the output to the input generated by an atrial extrastimulus. This extrastimulus scans electrical diastole of the heart to enable output to be plotted against input. Using this technique, we compared two mathematical models of the AVN, a rectangular hyperbola and a decaying exponential, respectively. The models were compared in 40 curves from 32 patients with only one AVN transmission pathway. Standard errors of the estimate were usually (25/40 trials) less with the exponential model, suggesting this the preferred algorithm for further development.

Examination of an exponential model of conduction through the human atrioventricular node.

The atrioventricular node (AVN) has been modeled by relating output (A2H2 or H1H2) to input (A1A2) where A and H are atrial and His bundle electrograms during fixed rate atrial pacing (A1A1) or with an extrastimulus (A2). (Formula: see text) This study examined this model in 61 nonselected patients, specifically for AVN (in)stability and the possibility of multiple pathways. After programmed atrial stimulation at two basic cycle lengths of 600 ms and 462 ms, A1H1, A2H2 and H1H2 were digitized and plotted as a function of A1A2. Seven of 104 trials were rejected as SD. A1H1 was greater than 15 ms, suggesting AVN instability. Another 26 and 34 plots, respectively, of A2H2 and H1H2 were rejected because of inadequate data. In the remainder, goodness of fit of the single exponentials was tested statistically in three ways: R2, the runs test, and the Kendall rank coefficient test. Results were compared with an electrophysiologist who examined plots for one or more pathways (either discontinuous curves or slope change in a continuous curve). Single exponentials were successfully fitted (by runs test) in 44/71 and 34/63 of A2H2 and H1H2 plots, respectively, usually in accordance with the cardiologist. Discordance between computations and the cardiologist could be attributed to data scatter and lack of a sufficiently rigid stimulation protocol. The identification of bifurcation points in the presence of multiple pathways, particularly when manifest as a change in slope (approximately 6% of trials) rather than discontinuity of plots (approximately 20% of trials) remains an outstanding problem.

Fast algorithms for the analysis of sino-atrial node function.

The calculations of parameters of the sino-atrial node function have previously required the application of a non-linear least squares curve-fitting algorithm. We have compared five algorithms, three of which eliminate the need for direct non-linear least squares routines. The fast algorithms can provide greater accuracy while using less than 10% of the computing time. They make it feasible to provide real-time analysis during clinical electrophysiological studies.

Multiple circus movement tachycardias with multiple accessory pathways.

A patient with the Wolff-Parkinson-White syndrome manifesting four types of tachycardia is described. The location and the participation during tachycardia of two different types of accessory atrioventricular pathways were documented during a programmed stimulation study. Unusual modes of initiation of tachycardias were observed, such as the initiation of an orthodromic circus movement tachycardia by an atrial premature beat that conducted in anterograde direction down the accessory pathway.

Value of the 12 lead electrocardiogram in diagnosing type and mechanism of a tachycardia: a survey among 22 cardiologists.

Information from programmed electrical stimulation of the heart has improved our ability to diagnose the site of origin and mechanism of a tachycardia from the 12 lead electrocardiogram. To test this hypothesis, the 12 lead electrocardiograms of a 12 year old girl with the Wolff-Parkinson-White syndrome showing four different types of tachycardia were sent for interpretation to 30 leading electrocardiologists , 22 of whom responded. A correct diagnosis of all four tachycardias was made by 13. Three or two of the tachycardias were correctly diagnosed by four and five cardiologists, respectively. The outcome of our study indicates that the pathway and mechanism of tachycardia can frequently be predicted from the 12 lead electrocardiogram alone.

Ventricular standstill despite normal electrophysiology study: a further possible indication for pacing.

Permanent pacing has usually been indicated for the treatment of organic disease of the sinus node or specific cardiac conducting tissue. We report three patients in whom profound syncope was apparently related to intense, transient autonomic dysfunction. Although ventricular standstill was documented in all three, detailed electrophysiology study, responses to graded Valsalva manoeuvres and carotid sinus massage, and repeated observations after cardiac autonomic blockade by IV atropine (0.03 mg/Kg) and propranolol (0.15 mg/Kg) were essentially normal. Permanent ventricular (VVI) pacing has controlled symptoms in all three, over follow-up period of 20 to 26 months. These observations suggest that transient autonomic imbalance may be a cause of undiagnosed cardiac syncope. This is neither excluded by normal electrophysiology study nor by normal responses to usual provocative autonomic interventions.

[Investigation of the preexcitation syndromes]. / Untersuchung des Präexzitationssyndroms.

Assessment of the localization and function of accessory atrioventricular pathways may be undertaken with noninvasive and invasive examination techniques. Noninvasive methods, however, such as electrocardiography, vectorcardiography, precordial mapping, echocardiography and scintigraphy do not enable exact delineation of the site of the accessory pathway since, in general, their use requires maximal preexcitation; moreover, they are of less value in the presence of septal bundles, multiple accessory pathways or intraventricular conduction disturbances. Accordingly, localization of accessory atrioventricular pathways is based on data obtained from intracardiac electrography such as the interval between stimulus and delta wave during atrial pacing, retrograde atrial sequence, VA conduction time at onset of right or left bundle branch block as well as responses to programmed ventricular stimulation during orthodromic reciprocating tachycardia. The most exact method for determination of the localization of the Kent bundle employs intraoperative endocardial and epicardial mapping with analysis of VA and AV conduction times during reciprocating tachycardia, ventricular stimulation and atrial pacing. The conduction properties of the accessory atrioventricular bundle may be estimated noninvasively based on the persistence of a delta wave as a function of the heart rate, the influence of antiarrhythmic agents on the anterograde conduction via the normal pathway as well as the shortest interval between two consecutive QRS complexes with delta waves during atrial fibrillation. Functional assessment is carried out invasively through recording the anterograde and retrograde refractory periods of the Kent bundle as well as observations during programmed atrial and ventricular stimulation or induced atrial fibrillation.

The antiarrhythmic effect of intravenous disopyramide in an open study.

The antiarrhythmic effect of intravenous disopyramide phosphate was assessed in a multicentre open study of 141 patients admitted to coronary care units. Disopyramide was administered in a bolus dose of 2 mg/kg over 10 min with an optional second bolus of 1 mg/kg and infusion of 0.4 mg/kg hour. Atrial fibrillation was terminated in 57% of 56 patients, supraventricular tachycardia in 82% of 11 patients, ventricular tachycardia in 88% of 17 patients and premature ventricular contractions were controlled in 85% of 55 patients. Atrial flutter was terminated in only 2 of 17 patients (12%). Side effects occurred in 38% of the patients, the most frequent being those relating to anticholinergic properties of the drug (15%) or systemic hypotension (13%). Occasionally worsening of the arrhythmia (4%), QRS widening (3) or apparent hypertension (2%) were noted. It was concluded that intravenous disopyramide is an effective antiarrhythmic agent in the coronary care unit setting, but that side effects require close monitoring of dosage.

beta-Blockade in acute myocardial infarction. Inability of relatively late administration to influence infarct size and arrhythmias.

The effects of orally administered timolol maleate (10 mg twice a day) were assessed in 88 patients entered into a double-blind study within 10.74 +/- 5.07 hours of onset of myocardial infarction. Timolol maleate produced no significant change in crude mortality rate, infarct size, incidence of arrhythmias or significant left ventricular failure. Withdrawals from study because of recurrent angina or hypertension were confined to the placebo group. The results of this study suggested that, when given relatively late after infarction, timolol maleate does not reduce either infarct size or incidence of arrhythmias, despite production of a safe and effective beta-blockade.

Appraisal of factors influencing the normal sinus node recovery time.

The normal period of depression of sinoatrial node automaticity (sinus node recovery time, SNRT) following one minute of overdrive right atrial pacing was evaluated in 34 subjects, aged 27--83 years. Specific attention was paid to the influence of the patient's heart rate, atrial pacing rate (100 and 130 bpm) and site, and of vagal and sympathetic effects, as assessed by observations following the administration of atropine, 0 . 03 mg/kg, and propranolol, 0 . 15 mg/kg. Normal SNRT was 1046 +/- 17 ms at 100 bpm and 980 +/- 19 ms at 130 bpm. Linear regression analysis showed that at pacing rates of both 100 and 130 bpm, both before and after autonomic block, a highly significant relation existed between SNRT and the stable P-P interval observed after cessation of pacing. These regression equations were used to develop a correction factor for cycle length in assessing SNRT (corrected SNRT = SNRT--0 . 86 X cycle length, where 0 . 86 was the slope of the regression equation). The mean corrected SNRT was 314 +/- 10 ms and 290 +/- 8 ms at 100 and 130 bpm, respectively. Vagal influences increased SNRT and were of greater magnitude than the decrease in SNRT due to sympathetic effects. Corrected SNRT was significantly longer following left atrial than following right atrial pacing, but in those eight patients studied, was not significantly different following right atrial or right ventricular stimulation.