Predictors of angiographic findings when chest pain recurs after successful coronary angioplasty.

The angiographic findings of 569 patients who underwent repeat coronary angiography for recurrence of chest pain after successful coronary angioplasty were evaluated. On the basis of angiographic findings, 250 patients (44%) were classified as having restenosis, 72 (13%) incomplete revascularization, 115 (20%) new significant coronary artery lesions, and 132 (23%) no significant disease. The number of diseased vessels at the time of coronary angioplasty (P < 0.001), number of vessels dilated (P < 0.001), and in particular, the time from angioplasty to recurrent chest pain (P < 0.001), were predictive of angiographic findings. When chest pain recurred within 4 weeks of angioplasty, 70% of patients had either incomplete revascularization or no significant coronary artery stenosis, when it recurred between 4 and 24 weeks of angioplasty, restenosis was the most common finding (71%), and when it recurred more than 24 weeks after angioplasty, new disease was the most common finding, occurring in 53% of patients. Of the 115 patients who developed new disease, angioplasty was initially performed on 133 vessels, and 222 vessels were not dilated. At repeat angiography, 81 of the 133 vessels (61%) that had had angioplasty and 109 of the 222 vessels (49%) that had not had angioplasty had new lesions; this difference was significant at P = 0.03. In conclusion, although the most common cause of recurrence of chest pain after initially successful coronary angioplasty was restenosis, other mechanisms may also be responsible. The time from coronary angioplasty to onset of recurrent chest pain was the most powerful predictor of angiographic outcome. The incidence of new lesion development was higher in the vessels that had instrumented angioplasty, possibly reflecting accelerated atherosclerosis or increased fibrocellular proliferation from intimal injury.

'Tandem lesion' coronary angioplasty: ten years' experience.

BACKGROUND: To evaluate the acute and long-term results of 'tandem lesion' coronary angioplasty in the left anterior descending artery, and to identify the determinants of restenosis. METHODS: A retrospective analysis of clinical, angiographic, and procedure-related variables was carried out on a consecutive series of 102 patients (mean age 54 years, range 34-71 years; 77% men) who had undergone tandem lesion coronary angioplasty in the left anterior descending artery (204 lesions) between 1981 and 1991. RESULTS: Angiographic success was achieved in 96 patients (94%) and 195 lesions (96%). Clinical success was achieved in 91 patients (89%). Five patients (5%) suffered a non-fatal Q-wave myocardial infarction. No procedural deaths occurred. Complete follow-up data were available for all 102 patients (median 46 months, range 1-122 months). During the follow-up period, two patients (2%) died, two (2%) suffered non-fatal myocardial infarction, and 18 (18%) underwent a second revascularization procedure. The cumulative probability of survival was 98.9% and 97.8% at 1 and 5 years respectively. Survival free from myocardial infarction, bypass surgery and repeat angioplasty at 1 and 5 years was 80.8% and 74.9% respectively. Thirty patients underwent repeat angiography (mean 8.8 months) for symptoms or evidence of reversible ischaemia. Restenosis occurred at a single dilated site in 14 patients and at both sites concurrently in six patients. Eight patients had no restenosis but two had total occlusion of the left anterior descending artery. Multiple logistic regression analysis identified increased inflation frequency as the only independent predictor of restenosis. CONCLUSIONS: Tandem lesion coronary angioplasty of the left anterior descending artery can be performed with a high primary success rate and favourable long-term outcome. The fact that restenosis occurred at a single site more often than at both, suggests that systemic factors are less important than local factors in influencing restenosis.

Percutaneous transluminal coronary angioplasty in patients 70 years of age or older: 12 years' experience.

OBJECTIVE: To evaluate the short and long term results of coronary angioplasty in patients aged 70 years and older and identify the determinants of long-term survival. DESIGN: A retrospective analysis of clinical, angiographic, and procedure related variables on a consecutive series of patients. PATIENTS: 163 patients aged 70 years and older (mean (range) age 73 (70-83) years; 63% men) who underwent a first coronary angioplasty procedure between 1981 and 1993. RESULTS: Procedural success was achieved in 82% of patients. Four patients (2%) died, three (2%) had a myocardial infarction, and five (3%) underwent emergency coronary artery bypass surgery. Complete follow up data were available for all patients (median (range) 35 (2-146) months). During the follow up period 16 patients (10%) died, two (1%) suffered non-fatal myocardial infarction, and 12 (7%) underwent elective coronary artery bypass surgery. A second angioplasty procedure was performed in 24 patients (15%). The cumulative probability of survival was 90.7% at 1 year and 83.4% at 5 years. Survival free from myocardial infarction, bypass surgery, and repeat angioplasty at 1 and 5 years was 68.2% and 56.0%, respectively. Proportional hazards regression analyses identified incomplete revascularisation as the only independent predictor of poorer overall survival (P = 0.04) and event free survival (P < 0.001). At census, of the 143 survivors, 75 (52%) were asymptomatic, 58 (41%) had mild angina, and only 10 (7%) complained of grade III or IV angina. Some 112 patients (78%) improved by at least two angina grades. CONCLUSION: Coronary angioplasty can be performed safely in the elderly and provides good symptomatic relief and favourable long-term outcome. Complete revascularisation may not be necessary if the primary goal is to achieve symptomatic relief, but incomplete revascularisation is associated with poorer long-term survival.

Percutaneous transluminal coronary angioplasty of aorta ostial, non-aorta ostial, and branch ostial stenoses: acute and long-term outcome.

The acute and long-term outcome of 198 patients who underwent coronary angioplasty of ostial stenoses was evaluated. Procedural success was achieved in 85% of aorta ostial stenoses, 90% of non-aorta ostial stenoses, and 87% of branch ostial stenoses (P = 0.84). A major complication occurred in 5.9%, 6.3%, and 6.9% of patients who underwent aorta ostial, non-aorta ostial, and branch ostial stenosis angioplasty, respectively (P = 0.97). A greater residual stenosis (P = 0.005) resulted from angioplasty of aorta ostial lesions despite a greater inflation frequency (P < 0.001), inflation pressure (P < 0.001), and total inflation duration (P < 0.001). The restenosis rate was higher for aorta ostial lesions (71%) when compared to non-aorta ostial (60%) and branch ostial lesions (32%) (P = 0.01). However, since the denominator included only the 49% who returned for repeat coronary angiography, the exact angiographic restenosis rate cannot be determined. The cumulative probability of survival was 99% at 1 year and 93% at 3 years. The 1 and 3 year freedom from death, myocardial infarction, bypass surgery, and repeat angioplasty was 70% and 57%, respectively. At census, 57% were asymptomatic, and only 9% suffered severe angina. Coronary angioplasty of ostial stenoses can be carried out with an acceptable success and complication rate, and provides good symptomatic relief and favourable long-term outcome. Randomized trials to compare new angioplasty technology with balloon angioplasty will be necessary to select the best device therapy for ostial lesions.

Efficacy of a third coronary angioplasty for a second restenosis: short-term results, long-term follow up, and correlates of a third restenosis.

OBJECTIVE: To report on the short-term and long-term results of patients who underwent a third coronary balloon angioplasty for a second restenosis and to identify the correlates of a third clinical restenosis. DESIGN: A retrospective analysis of clinical, angiographic, and procedure related variables of a consecutive series of patients. PATIENTS: 62 patients (mean (range) age 53 (31-72) years; 84% men) who underwent a third coronary balloon angioplasty of a single coronary artery segment at which restenosis had occurred after two previous angioplasty procedures between 1986 and 1992. RESULTS: Procedure success was achieved in 56 patients (90%). Complications included one myocardial infarction (2%) and one emergency coronary artery bypass surgery (2%). Complete follow up data were available (median (range) 48 (12-94) months). During the follow up period, four patients (6%) died, two (3%) had a non-fatal myocardial infarction, and five (8%) underwent elective coronary artery bypass surgery. Nine patients (14%) underwent a fourth angioplasty for a third clinical restenosis, and three (5%) had a fourth angioplasty procedure for new coronary lesions. The cumulative probability of survival for all 62 patients was 97% and 95% at 1 and 5 years, respectively. The 1 and 5 year freedom from death, infarction, bypass surgery, and repeat angioplasty was 82% and 66.6%, respectively. At census, of the 58 survivors, 31 (53%) were asymptomatic and only eight (14%) complained of angina grade III or IV (P < 0.001). A third clinical restenosis occurred in 22 (39%) of the 56 patients who had initially successful procedures. Multiple stepwise logistic regression analysis identified the interval between the second and third angioplasty procedure as the only independent predictor of a third clinical restenosis (P = 0.004). CONCLUSIONS: A third coronary angioplasty for a second restenosis can be performed safely and effectively and should be considered as an integral part of the overall coronary angioplasty revascularisation strategy. The incidence of a third clinical restenosis remains high, however, and is correlated with the interval between the previous angioplasty procedures.

Clinical and lesion morphologic determinants of coronary angioplasty success and complications: current experience.

OBJECTIVES: This study evaluated the validity of the American College of Cardiology/American Heart Association ABC lesion classification scheme and its modifications. BACKGROUND: With the continued refinement in angioplasty technique and equipment evolution, the lesion morphologic determinants of immediate angioplasty outcome have changed significantly. Hence, the validity of the classification scheme has been questioned. METHODS: We assessed the lesion morphologic determinants of immediate angioplasty outcome in 729 consecutive patients who underwent coronary angioplasty of 994 vessels and 1,248 lesions. RESULTS: Angioplasty success was achieved in 91% of lesions, and abrupt closure occurred in 3%. Success was achieved in 96%, 93% and 80% of type A, B and C lesions, respectively (A vs. B, p = NS; B vs. C, p < 0.001; A vs. C, p < 0.001; A vs. B1, p = NS; A vs. B2, p = 0.03; B1 vs. B2, p = 0.02; B2 vs. C, p < 0.001; C1 vs. C2, p = NS). Abrupt closure occurred in 2.1%, 2.6% and 5% of type A, B and C lesions, respectively (A vs. B, B vs. C, A vs. C and A vs. B1, all p = NS; B1 vs. B2, p = 0.01; B2 vs. C1, p = NS; C1 vs. C2, p = 0.04). Type B characteristics had a success rate ranging from 74% to 95% and an abrupt closure rate ranging from 2.2% to 14%. Type C characteristics had a success rate ranging from 57% to 88% and an abrupt closure rate ranging from 0% to 16%. Longer lesions, calcified lesions, diameter stenosis of 80% to 99% and presence of thrombus were predictive of a lower success rate. Longer lesions, angulated lesions, diameter stenosis of 80% to 99% and calcified lesions were predictive of an abrupt closure. CONCLUSIONS: The previously proposed classification schemes are outdated and need to be changed for application in current angioplasty practice. Analyzing specific lesion morphologic characteristics rather than applying a simple lesion classification score when evaluating angioplasty outcome may be more useful because it provides a more precise profile of the lesion and allows better patient stratification and selection.

Health service costs of coronary angioplasty and coronary artery bypass surgery: the Randomised Intervention Treatment of Angina (RITA) trial.

For some patients with coronary artery disease, percutaneous transluminal coronary angioplasty (PTCA) is an alternative to coronary artery bypass grafting (CABG). We report comparative health service costs of these interventions within the Randomised Intervention Treatment of Angina (RITA) trial. Medications were costed at published UK prices; other resource use was costed with a set of unit costs estimated at two recruiting centres to the RITA trial, one in London and one outside. Over 2-year follow-up of 1011 patients, the estimated mean additional cost for those randomised to CABG compared with PTCA was 1050 pounds (95% CI 621 pounds-1479 pounds), with unit costs from the non-London centre, and 1823 pounds (1202 pounds-2444 pounds), with unit costs from the London centre. The initial average cost of treating a patient randomised to PTCA is about 52% of that of CABG, but after 2 years this increased to about 80% because of the greater need for subsequent interventions. The balance of advantage between PTCA and CABG may change after several years: funding has been obtained to continue RITA follow-up for 10 years. However, on the basis of patients' status at 2 years, the cost advantages of PTCA cannot be ignored. Further research is necessary to assess whether the advantage of PTCA in terms of cost is translated into one of cost-effectiveness.

Comparison of biphasic and monophasic waveforms in epicardial atrial defibrillation.

OBJECTIVES: Because biphasic waveforms have previously been shown to be more efficient than monophasic waveforms in defibrillation of the ventricle, we compared the efficiency of the two waveforms in defibrillation of the atria. BACKGROUND: The development of an implantable atrial defibrillator would offer significant advantages over current approaches to the management of atrial fibrillation. Patient tolerance of atrial shocks from such a device, however, would depend critically on the deployment of an efficient waveform. METHODS: Both the monophasic and biphasic shocks were of 8-ms duration, and the biphasic was a dual-capacitor waveform with equal first- and second-phase duration and leading-edge voltage. One hundred randomized atrial shocks were evaluated in 21 patients during cardiopulmonary bypass. Atrial fibrillation was induced by the application of alternating current. Atrial shocks were delivered through customized, contoured epicardial paddles applied to the posterior left atrial wall (surface area 11 cm2) and to the anterior right atrial wall (surface area 26 cm2). RESULTS: For the monophasic waveform the delivered energy (joules) associated with 50% success (E50) was 1.44 J (95% confidence interval [CI] 0 to 11.2) and with 80% (E80) success 3.9 J (95% CI 2.42 to 109.8); for the biphasic waveform 50% success was achieved with 0.37 J (95% CI 0.36 to 0.38) (p = NS) and 80% success with 0.57 J (95% CI 0.56 to 0.58) (p < 0.05). CONCLUSIONS: A biphasic waveform is more efficient than a monophasic waveform in atrial defibrillation. This may have implications for the development of an implantable atrial defibrillator for paroxysmal atrial fibrillation in addition to improvement of elective transthoracic and endocardial cardioversion of chronic atrial fibrillation.

Variability of left atrial bloodflow predicts intolerance of ventricular demand pacing and may cause pacemaker syndrome.

Variability of left and right atrial and left ventricular bloodflow was studied using transthoracic and transesophageal Doppler echocardiography and related to pacemaker mode preference during everyday activity. Bloodflow variability was less at all sites during dual chamber pacing compared to single chamber pacing. However, in patients suffering from pacemaker syndrome and who prefer DDDR pacing, significantly increased variability of left atrial antegrade (but not retrograde) bloodflow during VVIR pacing compared to DDDR pacing was noted, which was not evident in patients tolerating VVIR mode pacing. This effect was not detected at any other site and suggests that adverse left atrial hemodynamics may result in intolerance to VVI/R mode pacing and might cause pacemaker syndrome.

Percutaneous transluminal coronary angioplasty in patients with prior coronary artery bypass grafting: ten years' experience.

We evaluated the acute and long-term results of percutaneous transluminal coronary angioplasty in 140 patients with prior coronary artery bypass grafting treated over a 10-year period (1981-1991). Angioplasty was technically successful in 85% of 122 nonoccluded native vessels and in 86% of 50 saphenous vein grafts. Two patients (1.4%) had a myocardial infarction and there were three procedure-related deaths (2.1%). The cumulative probability of survival was 91.5% and 74.5% at 1 and 5 years, respectively. Survival free from myocardial infarction and repeat bypass grafting at 1 and 5 years was 77.3% and 53.9%, respectively. At census, 31% of the 117 survivors were asymptomatic, and 47% were improved by at least two angina grades. Coronary angioplasty provides an apparently safe and effective alternative method of revascularization in selected patients with prior coronary artery bypass grafting. This treatment strategy potentially avoids reoperation with its attendant risks.

Determinants of success of coronary angioplasty in patients with a chronic total occlusion: a multiple logistic regression model to improve selection of patients.

OBJECTIVE: To study the determinants of success of coronary angioplasty in patients with chronic total occlusions, and to formulate a multiple logistic regression model to improve selection of patients. DESIGN: A retrospective analysis of clinical and angiographic data on a consecutive series of patients. PATIENTS: 312 patients (mean age 55, range 31 to 79 years, 86% men) who underwent coronary angioplasty procedure for a chronic total occlusion between 1981 and 1992. RESULTS: Procedural success was achieved in 191 lesions (61.2%). A major complication occurred in six patients (1.9%). Multiple stepwise logistic regression analysis identified the presence of bridging collaterals (p < 0.001), the absence of a tapered entry configuration (p < 0.001), estimated duration of occlusion of greater than three months (p = 0.001), and a vessel diameter of less than 3 mm (p = 0.003) as independent predictors of procedural failure. The logistic regression model was used to classify patients into groups of high, intermediate, and low probability of procedural success with cut off points of 70% and 30%. The predictive value for procedural success (probability > or = 70%) was 91% (95% confidence intervals (95% CI) 83% to 96%) and predictive value for procedural failure (probability < 30%) was 81% (95% CI 64% to 92%). CONCLUSIONS: Percutaneous transluminal coronary angioplasty of chronic total occlusions is associated with a low risk of acute complication. Procedural success is influenced by easily identifiable clinical and angiographic features and the multiple regression model described may help to improve selection of patients.

Echocardiographic description of the CarboMedics bileaflet prosthetic heart valve.

OBJECTIVES: The aim of this study was to describe the echocardiographic appearance of the normal CarboMedics prosthesis in the aortic and mitral positions. BACKGROUND: Echocardiography is the standard method of assessing prosthetic valves. However, new valve designs may still be marketed without an accompanying echocardiographic description. The CarboMedics prosthesis is in widespread use, but few noninvasive hemodynamic data have been published. METHODS: Echocardiography was performed in 147 patients with a total of 96 normally functioning CarboMedics prostheses in the aortic position and 75 in the mitral position; in 24 patients, valves were implanted in both positions. The following variables were measured: peak and mean transvalvular velocities, peak and mean instantaneous gradient estimated from the modified Bernoulli equation, aortic acceleration slope, pressure half-time, transvalvular flow and effective orifice area using the continuity equation. Patterns of regurgitation were observed by transthoracic study in all valves and by transesophageal study in selected mitral valve prostheses. RESULTS: For the aortic valve prostheses, estimated mean gradient ranged between 6 and 19 mm Hg. Effective area differed markedly among the anulus diameters (p < 0.001), with a mean value of 1 cm2 for the 19-mm valve and 2.6 cm2 for the 29-mm valve. For the mitral valve prostheses, mean gradient ranged from 3 to 7 mm Hg. There were a total of four washing leaks, one on either side of each pivotal point, and these lasted throughout systole or diastole. One jet was commonly more prominent than the other three. CONCLUSIONS: The CarboMedics prosthesis offered relatively little resistance to forward flow except at small anulus diameters. The washing jets were prominent and would be easy to misdiagnose as a sign of paraprosthetic regurgitation.

Comparative long-term results of coronary angioplasty in single and multivessel disease.

The comparative long-term clinical results of coronary angioplasty in 448 patients with single-vessel and 451 patients with multivessel disease are reported. Clinical status was determined at census for 898 patients (99.9%). Actuarial survival at 5 years was 92.7% for single-vessel and 85.6% for multivessel disease patients (relative risk 2.1). Patients with multivessel disease had higher rates of cardiac death and non-fatal myocardial infarction (relative risk 1.8), and coronary artery bypass surgery (relative risk 2.5) than patients with single-vessel disease. At follow-up 72.6% of single-vessel and 61.3% of multivessel disease patients had no angina and 43.3% and 35.8%, respectively, were taking no regular anti-anginal medication. Treatment by coronary angioplasty is associated with a good long-term prognosis, but survival and event-free survival rates are lower in patients with multivessel disease than in patients with single-vessel disease, even after correction for differences in other baseline characteristics.

The Hatle orifice area formula tested in normal bileaflet mechanical mitral prostheses.

The Hatle formula was derived empirically in native mitral stenosis and may not be valid for normal prosthetic valves. Bileaflet mechanical prostheses open fully at low flows and have minimal interindividual variation in orifice area. In these valves effective area and measured manufacturer's area should be similar. We studied 60 patients aged 58 +/- 12 yr at a mean of 5 months after implantation with a CarboMedics prosthesis. There was a coexistent aortic prosthesis in 21. All diastolic measurements were averaged over 5 beats and stroke volume was calculated from the integral of the subaortic velocity trace and the cross-sectional area of the left ventricular outflow tract. For the whole group, area by the Hatle formula was 3.1 +/- 0.7 cm2 and measured area was 2.8 +/- 0.4 cm2. There was no significant correlation between these values (p = 0.329). Pressure half-time was more closely correlated with peak transmitral velocity (p = 0.012), RR interval (p = 0.015), diastolic time interval (p = 0.062) and stroke volume (p = 0.074). We conclude that the Hatle formula should not be applied to normal bileaflet mitral prostheses where pressure half-time reflects nonprosthetic factors more closely than orifice area.

The effect of atrio-ventricular delay programming in patients with DDDR pacemakers.

Modern DDDR (dual chamber universal, rate responsive) pacemakers are complex, hugely capable devices incorporating new features that theoretically should enhance haemodynamics and therefore quality of life. Ten patients (mean age 48 years) with chronotropic incompetence and high grade A-V block had activity sensing DDDR devices implanted and underwent a randomized double-blind crossover assessment of rate responsive and different fixed atrio-ventricular delay (AVD) settings during 2 weeks of out-of-hospital activity in DDDR mode. Subjective assessment showed improved 'general wellbeing' and preference for 175 ms rate responsive AVD (P less than 0.01) or 125 ms fixed AVD (P less than 0.05). The longest fixed AVD setting (250 ms) was least acceptable and had increased symptom prevalence (P less than 0.02). Perceived exercise capacity and exercise treadmill tolerance was not significantly different at any setting in DDDR mode but was less in DDD mode. Echocardiographically derived stroke distance was greater at 125 ms AVD than 250 ms at 100 b.min-1 (P less than 0.05) but did not differ at slower heart rates at any AVD. Colour Doppler assessed mitral and tricuspid regurgitation was greatest at 250 ms AVD at all heart rates but did not correlate with increased symptomatology. Stroke distance evaluated from the mitral inflow velocity profile allows improved AVD programming during DDDR pacing. Rate adaptive A-V delay is a useful feature during DDDR pacing.

"Subclinical" pacemaker syndrome: a randomised study of symptom free patients with ventricular demand (VVI) pacemakers upgraded to dual chamber devices.

OBJECTIVE: To determine whether symptom free patients with single chamber pacemakers benefit from dual chamber pacing. DESIGN: A randomised double blind crossover comparison of ventricular demand (VVI), dual chamber demand (DDI), and dual chamber universal (DDD) modes after upgrading from a VVI device. SETTING: Cardiology outpatient department. PATIENTS: Sixteen patients aged 41-84 years who were symptom free during VVI mode pacing for three or more years. INTERVENTION: Pacemaker upgrade during routine generator change. MAIN OUTCOME MEASURES: Change in subjective (general health perception, symptoms) and objective (clinical assessment, treadmill exercise, and radiological and echocardiographic indices) results between pacing modes before and after upgrading. RESULTS: 75% preferred DDD, 68% found VVI least acceptable with 12% expressing no preference. Perceived general well-being and exercise capacity (p less than 0.01) and treadmill times (p less than 0.05) were improved in DDD mode but VVI and DDI modes were similar. Clinical, echocardiographic, radiological, and electrophysiological indices confirmed the absence of overt pacemaker syndrome, although mitral and tricuspid regurgitation was greatest in VVI mode (p less than 0.01). CONCLUSIONS: Most patients who were satisfied with long term pacing in VVI mode benefited from upgrading to DDD mode pacing suggesting the existence of "subclinical" pacemaker syndrome in up to 75% of such patients. The DDI mode offered little subjective or objective benefit over VVI mode in this population and should be reserved for patients with paroxysmal atrial arrhythmias. VVI mode pacing should be used only for patients with very intermittent symptomatic bradycardia or atrial fibrillation with a good chronotropic response during exercise.

Long-term results of coronary angioplasty for single vessel, proximal, left anterior descending disease.

The acute and long-term results of coronary angioplasty in 295 patients with isolated, proximal left anterior descending coronary stenosis are reported. The angiographic success rate was 83.4% overall, but 90.5% for non-occluded arteries treated since 1985. Clinical success at hospital discharge was achieved in 79.7%. The median duration of follow-up was 2.9 years and vital status was established in 99.7% at census. Cumulative 5-year cardiac survival was 96.2% after successful angioplasty and 95.6% for all patients. Five-year freedom from all cardiac events including cardiac death, myocardial infarction and repeat intervention was 73.8% amongst successfully treated patients, and 63.0% for all patients. After angioplasty, patients had less angina, required less anti-anginal medication and were more likely to be in gainful employment. Our data indicate that coronary angioplasty is an effective long-term treatment for selected patients with single vessel disease involving the proximal left anterior descending coronary artery.

The continuity equation tested in a bileaflet aortic prosthesis.

The continuity equation is valid for a population of aortic valves, but its accuracy in individual valves is uncertain. In bileaflet prostheses, obstruction to forward flow is small and individual variability in opening behaviour is minimal. In these valves, the area of the effective orifice should be close to that measured by the manufacturer. A total of 57 patients aged 58 +/- 11 years were studied at a mean of 3.6 months after implantation with a CarboMedics aortic prosthesis. Nine had additional implants in the mitral position and all prostheses were clinically normal. Peak subaortic and transaortic velocities were averaged over 5 beats. The area of the effective orifice was significantly different between the four diameters (P less than 0.00001), and the correlation between the effective and measured area of the orifice was moderate (rs = 0.73, P less than 0.00003). The 95% range for the differences between individual pairs of values, however, was 0.16 +/- 0.61 cm2. Discrepancies probably arose in the estimation of subaortic cross-sectional area and subaortic velocity. Thus, the continuity equation may be inaccurate in an individual prosthetic valve when functioning normally.

A randomized double-blind crossover comparison of four rate-responsive pacing modes.

The aim of this study was to compare, both subjectively and objectively, four modern rate-responsive pacing modes in a double-blind crossover design. Twenty-two patients, aged 18 to 81 years, had an activity-sensing dual chamber universal rate-responsive (DDDR) pacemaker implanted for treatment of high grade atrioventricular block and chronotropic incompetence. They were randomly programmed to VVIR (ventricular demand rate-responsive), DDIR (dual chamber demand rate-responsive), DDD (dual chamber universal) or DDDR (dual chamber universal rate-responsive) mode and assessed after 4 weeks of out-of-hospital activity. Five patients, all with VVIR pacing, requested early reprogramming. The DDDR mode was preferred by 59% of patients; the VVIR mode was the least acceptable mode in 73%. Perceived "general well-being," exercise capacity, functional status and symptoms were significantly worse in the VVIR than in dual rate-responsive modes. Exercise treadmill time was longer in DDDR mode (p less than 0.01), but similar in all other modes. During standardized daily activities, heart rate in VVIR and DDIR modes underresponded to mental stress. All rate-augmented modes overresponded to staircase descent, whereas the DDD mode significantly underresponded to staircase ascent. Echocardiography revealed no difference in chamber dimensions, left ventricular fractional shortening or pulmonary artery pressure in any mode. Cardiac output was greater at rest in the dual modes than in the VVIR mode (p = 0.006) but was similar at 120 beats/min. Beat to beat variability of cardiac output was greatest in VVIR mode (p less than 0.0001), with DDIR showing greater variability than DDD or DDDR modes (p less than 0.05). Mitral regurgitation estimated by Doppler color flow imaging was similar in all modes, but tricuspid regurgitation was significantly greater in VVIR than in dual modes (p less than 0.03). Subjects who preferred the DDDR mode and those who found the VVIR mode least acceptable had significantly greater increases in stroke volume when paced in the DDD mode than in the ventricular-inhibited (VVI) mode at rest (22%) when compared with subjects who preferred other modes (2%, p = 0.03). No other objective variable was predictive of subjective benefit from any rate-responsive pacing mode. Thus, dual sensor rate-responsive pacing (DDDR) is superior objectively and subjectively to single sensor (VVIR, DDIR and DDD) pacing and subjective benefit from dual chamber rate-augmented pacing is predictable echocardiographically.

Hemodynamic consequences of arrhythmias.

Hemodynamic effects during arrhythmias may be caused by underlying pathology (i.e., infarction) as well as disturbance of rate or conduction pattern. In all arrhythmias, compensatory mechanisms tend to restore normal hemodynamics, and with good left ventricular function this can be achieved despite wide disturbance of rhythm. Hemodynamic effects of ectopic beats can result in dramatic fall of stroke volume and reduction in cardiac output, which is greater for ventricular than for atrial ectopics. Prolonged tachycardias are also tolerated up to far higher rates (180/min) if they are atrial, not ventricular, in origin. Mean blood pressure is often maintained even when systolic pressure and cardiac output are reduced. Even in healthy young subjects it is possible for cardiac ischemia to be induced by excessive heart rates. Some of the most deleterious effects are produced by simultaneous atrial and ventricular contraction, which results in continued suppression of cardiac output, both during tachycardias and at normal heart rates. Such situations are often highly symptomatic. Few measurements are available during external chest compression, and these suggest only marginal improvement in hemodynamics, with low pressures and output.