The evaluation and management of atrial fibrillation (AF), the commonest of all cardiac arrhythmias, has been a long-standing challenge in cardiology. From the beginning of this century, research efforts have been directed at understanding the mechanistic basis of this disorder and developing effective therapies. In the past two decades there has been an exponential expansion in our knowledge base in both these areas. Important basic investigations and clinical studies have contributed to this progress. However, this has been accomplished by diverse groups of investigators, often from different specialties, without an opportunity to collate and assimilate this information. The development of a cohesive or shared strategy of overall research direction has been an important need in AF research and could result in more rapid advances in this field. Towards this end, the North American Society of Pacing and Electrophysiology (NASPE) and the National Heart, Lung and Blood Institute (NHLBI) collaborated in organizing a round table conference entitled, “Future Research Directions in Atrial Fibrillation” in Bethesda, Maryland on October 9, 1998. The deliberations of the workshop were the basis for this report developed by the writing committee in collaboration with the participants at the meeting. The writing group was specifically charged with performing a focused review of the current stateof-the-art, weighing the evidence and the discussions at the workshop, deliberating on the importance and relevance of the research, and identifying important new directions in AF research. It is the purpose of this report to summarize these efforts. The report is deliberately designed to be wide-ranging in scope but highly focused in recommendations with an overt attempt in prioritizing immediate and short-term research imperatives and long-term objectives. It is hoped that this document will provide a road map for future initiatives for researchers, funding agencies, technology developers, and health care professionals with an interest in AF.

Twenty-two years have elapsed since Andreas Gruentzig, MD, performed the first coronary angioplasty [(1,2)][1]. During that period, coronary angioplasty and its related procedures have evolved into a highly specialized cognitive and technical discipline, and the expectation of quality in coronary

Initial reports of percutaneous transluminal coronary angioplasty (PTCA) in the elderly (≥: 75 years) showed a significantly lower primary success rate, higher in‐hospital mortality, and a higher risk of emergency or elective coronary artery bypass graft (CABG) compared to younger patients. There are few data concerning acute outcomes and clinical follow‐up after the use of coronary stenting in the elderly compared to < the 75‐year‐old age group. We evaluated 82 elderly patients and 280 younger patients who received Palmaz‐Schatz stents during 1995, at a time when high pressure deployment and antiplatelet therapy was routinely used. The success rate and acute major complications were not significantly different between the elderly and younger patients. Clinical events (death, myocardial infarction [MI], repeat PTCA, or CABG) during 6‐month follow‐up were also not significantly different. Coronary stenting in the elderly can be carried out with a high success rate and low incidence of acute major complications. Thus, short‐term clinical outcomes in elderly patients appear similar to results obtained in younger patients.

A novel skin dose monitor was used to measure radiation incident on maximal X-ray exposed skin during 135 diagnostic and 65 interventional coronary procedures. For the diagnostic studies (n = 135), mean skin dose was 180 +/- 64 mGy; for PTCA (n = 35), it was 1021 +/- 674 mGy, single stents (n = 25) 1529 +/- 601 mGy, and multiple stents with rotational atherectomy (n = 5) 2496 +/- 1028 mGy. The dose independently increased with more cine runs, more fluoroscopy, and greater patient weight. Physicians should consider the potential for adverse radiation exposure when planning coronary interventional cases and deciding on the X-ray mode and angles used.

The purpose of this study was to determine the feasibility, safety and efficacy of elective deployment of a new coil-stent (KR stent) in patients with coronary artery disease. KR stent deployment was attempted in 100 patients (135 lesions) enrolled prospectively at a single centre from December 1996 to March 1997. Ten, 15, 18, 24, and 32 mm long KR stents were manually crimped onto balloons and deployed in native coronary artery lesions. Majority of the patients had recent acute coronary syndromes (unstable angina 30% and post-myocardial infarction angina 56%). Diabetes was present in 34 percent of the patients. Fifty-six percent had single-vessel and 44 percent multi-vessel disease. In 38 percent, the lesions were located in proximal segments and 40 percent of lesions were long. KR stents were successfully deployed in 98 percent of patients. Mean minimal luminal diameter increased by 2.89 +/- 0.63 mm (from 0.57 +/- 0.38 mm before to 3.45 +/- 0.56 mm after the procedure). Mean percent diameter stenosis decreased from 83.33 +/- 10.84 percent before to 3.38 +/- 5.74 percent after the stent deployment. Mean reference vessel diameter was 3.45 +/- 0.56 mm. There were occasional technical complications including balloon rupture (1), stent migration (2) and distal embolisation of atheromatous material (1). One patient developed subacute stent thrombosis. There were no other major in-hospital cardiovascular events. At the end of six-month follow-up, there were no myocardial infarction or death. Six patients presented with recurrence of symptoms within six-months of the procedure, four of whom underwent target vessel revascularisation procedure. In conclusion, the in-hospital and six-month follow-up clinical results were highly encouraging with KR stent. Successful deployment rates were high despite unfavourable clinical and angiographic background. Low clinical events on follow-up will make it suitable for elective stenting.

Objectives. We sought to determine the in-hospital clinical outcome and angiographic results of patients prospectively entered into the National Heart, Lung, and Blood Institute/New Approaches to Coronary Intervention (NHLBI/NACI) Registry who received Gianturco-Roubin stents as an unplanned new device.Background. Between August 1990 and March 1994, nine centers implanted Gianturco-Roubin flex stents as an unplanned new device in the initial treatment of 350 patients (389 lesions) who mere prospectively enrolled in the NHLBI/NACI Registry.Methods. Patients undergoing implantation of the Gianturco-Roubin flex stent were prospectively entered into the Gianturco-Roubin stent portion of the NHLBI/NACI Registry. Only subjects receiving the Gianturco-Roubin stent as a new device in an unplanned fashion are included.Results. The mean age of the patient group was 61.8 years, and the majority of the patients were men. A history of percutaneous transluminal coronary angioplasty (PTCA) was present in 35.4% of the group, and 16.9% had previous coronary artery bypass graft surgery. Unstable angina was present in 67.7%. Double- or triple-vessel coronary artery disease was present in 55.4%, and the average ejection fraction was 58%. The presence of thrombus was noted in 7.3%, and 7.2% had moderate to severe tortuosity of the lesion. The angiographic success rate was 92%. Individual clinical sites reported that 66.3% of the stents were placed after suboptimal PTCA, 20.3% for abrupt closure and 13.4% for some other technical PTCA failure. Major in-hospital events occurred in 9.7% of patients, including death in 1.7%, Q wave myocardial infarction in 3.1% and emergency bypass surgery in 6%. Abrupt closure of a stented segment occurred in 3.1% of patients at a mean of 3.9 days. Cerebrovascular accident occurred in 0.3%, and transfusion was required in 10.6%. Vascular events with surgical repair occurred in 8.6% of patients.Conclusions. Despite these complications, the use of this device for the treatment of a failed or suboptimal PTCA result remains promising given the adverse outcome of abrupt closure with conventional (nonstent) treatment.

This is the first detailed report from the Anglophone Caribbean of percutaneous transluminal coronary angioplasty (PTCA). The procedure resulted in complete dilatation of the occluded vessels in the five patients in whom it was undertaken, with significant improvement in exercise duration in the Bruce protocol (p < 0.001; 95% CI 2.5 to 4.1 minutes) in the four patients who were studied. PTCA can be undertaken in developing countries with limited resources, and should be offered to selected patients with symptomatic coronary artery disease who need a revascularisation procedure.

Coronary artery dimensions were evaluated in 42 patients (52 lesions) undergoing directional atherectomy of primary atheromatous lesions in native coronary arteries between October 1989 and April 1991, Dimensions were compared with a cohort of 162 patients (213 lesions) undergoing percutaneous transluminal coronary angioplasty of similar lesions between March 1984 and April 1988. Computer‐assisted quantitative angiography was performed for paired near‐orthogonal views (captured during diastole) of each treated lesion; image pairs taken prior to, immediately following, and 6 months after coronary intervention were studied. Although coronary dimensions were equivalent for the two treatment groups before therapy, the immediate posttreatment minimal lumen diameter was significantly larger after atherectomy than angioplasty (2.24 ± 0.53 mm vs 1.52 ± 0.34 mm, P < 0.01). Despite this, coronary dimensions were similar in the two groups at follow‐up angiography. Several dichotomous definitions of restenosis were tested using these quantitative data. Restenosis rates were similar for the two treatments using most definitions, but those definitions based on loss of relative or absolute lumen dimensions resulted in higher rates of restenosis following atherectomy. These data demonstrate that: (1) directional coronary atherectomy can achieve greater initial gain in luminal dimensions than angioplasty; (2) the loss in vessel dimensions within 6 months (late loss) is greater after atherectomy than after angioplasty; and (3) restenosis definitions rely on relative or absolute loss of initial luminal gain favor of angioplasty. (J Interven Cardiol 1996;9:121–127)

The field of cardiac pacing has expanded rapidly in recent years. Engineering improvements and microprocessor technology have resulted in a vast increase in pacemaker technology. The "high-tech" edge of cardiac pacing often discourages all but the pacemaker specialist from approaching a malfunctioning pacemaker. Electrocardiographic signs of pacemaker malfunction can be grouped into four categories: failure to output, failure to capture, undersensing, and inappropriate pacemaker rate. For each of these categories, there may be true malfunctions and pseudomalfunctions. In addition, environmental sources of electromagnetic interference, both within and outside the hospital environment, can result in pacemaker malfunction. Approaching pacemaker malfunction with these categories in mind should help minimize confusion.

Several techniques exist for percutaneous extraction of chronic pacemaker leads. To establish the efficacy of the Dotter retriever and pigtail catheter, we reviewed the removal of 59 endocardial pacemaker leads in 42 patients (mean age 71 years). The mean duration of lead implantation was 44 months (range 1–169 months). Thirty‐two leads were withdrawn with simple traction alone, and five leads were abandoned when traction failed. The remaining 22 leads were manipulated with a Dotter retriever or pigtail catheter, or both. Twelve leads were dislodged from the endocardium with simple traction (10)or with traction transmitted through an entwining pigtail catheter (2), but they could not be fully withdraivn. Eleven of these leads (92%)were then successfully extracted with the Dotter retriever. Seven of the remaining 10 leads were successfully disJodged and removed by the Dotter retriever. Overall, 9 of 12 leads (75%)that could not be dislodged from the endocardium with simple traction were removed with a Dotter retriever or pigtail catheter, or both. Three patients in whom no catheter method worked required thoracotomy for removal of infected leads. No complications resulted from use of the Dotter retriever or pigtail catheter. We conclude that the Dotter retriever and pigtail catheter have moderate efficacy for dislodging chronic endocardial leads. Once mobilized, however, the leads can be withdrawn with great success with the Dotter retriever. Newer technology should not result in the abandonment of this proven technique.

There has been increasing application of coronary angioplasty to patients with chronic total occlusions. The acute and long-term outcome in 271 patients after coronary angioplasty (142 single and 129 multiple stenoses) of a total occlusion was compared with 1,429 patients undergoing angioplasty of subtotal (less-than-or-equal-to 99% stenosis) occlusions (885 single and 544 multilesion) participating in the 1985-1986 National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry. Baseline characteristics were similar for each lesion group except for a higher incidence of prior myocardial infarction and left ventricular dysfunction (ejection fraction < 50%) in patients with total occlusion. Major complications (death, myocardial infarction or emergency bypass surgery) were similar (p = not significant) between patients with total and subtotal occlusions for single (6 vs 7%) and multilesion angioplasty (9 vs 6%).At 2 years, after making adjustments for baseline variables, patients with a total occlusion had a significantly increased risk of death compared with those with subtotal occlusion. There were no significant differences in cumulative event rates for myocardial infarction or bypass surgery. Approximately three-fourths of patients in each group were free of angina at 2 years. In conclusion, angioplasty of chronic total occlusions is associated with a similar acute complication rate. Despite similar relief of anginal symptoms, patients in the total occlusion group have a higher 2-year mortality.

Restenosis is a reparative response to arterial injury occurring with percutaneous coronary revascularization. However, the quantitative characteristics of the relation between vessel injury and the magnitude of restenotic response remain unknown. This study was thus performed to determine the relation between severity of vessel wall injury and the thickness of resulting neointimal proliferation in a porcine model of coronary restenosis.Twenty-six procine coronary artery segments in 24 pigs were subjected to deep arterial injury with use of overexpanded, percutaneously delivered tantalum wire coils. The vessels were studied microscopically 4 weeks after coil implantation to measure the relation between the extent of injury and the resulting neointimal thickness.For each wire site, a histopathologic score proportional to injury depth and the neointimal thicknesses at that site were determined. Mean injury scores were compared with both mean neointimal thickness and planimetry-derived area percent lumen stenosis. The severity of vessel injury strongly correlated with neointimal thickness and percent diameter stenosis (p < 0.001). Neointimal proliferation resulting from a given wire was related to injury severity in adjacent wires, suggesting an interaction among effects at injured sites.If the results in this model apply to human coronary arteries, restenosis may depend on the degree of vessel injury sustained during angioplasty.

Human coronary artery restenosis after percutaneous revascularization is a response to mechanical injury. Smooth muscle cell proliferation is a major component of restenosis, resulting in obstructive neointimal hyperplasia. Because ionizing radiation inhibits cellular proliferation, this study tested in a porcine coronary injury model the hypothesis that the hyperplastic response to coronary artery injury would be attenuated by X-irradiation.Deep arterial injury was produced in 37 porcine left anterior descending coronary artery segments with overexpanded, percutaneously delivered tantalum wire coils. Three groups of pigs were irradiated with 300-kV X-rays after coil injury: Group I (n = 10), 400 cGy at 1 day; Group II (n = 10), 400 cGy at 1 day and 400 cGy at 4 days and Group III (n = 9), 800 cGy at 1 day. Eight pigs in the control group underwent identical injury but received no radiation. Treatment efficacy was histologically assessed by measuring neointimal thickness and percent area stenosis.Mean neointimal thickness in all irradiated groups was significantly higher than in the control groups and thickness was proportional to X-ray dose.X-irradiation delivered at these doses and times did not inhibit proliferative neointima. Rather, it accentuated the neointimal response to acute arterial injury and may have potentiated that injury.

Directional coronary atherectomy (DCA) was performed in 158 patients over a 2-year period at the Mayo Clinic. Primary atheromatous lesions were treated in 92 patients (group 1) and restenosis lesions were treated in 66 (group 2). Technical success (recovery of tissue and greater than or equal to 40% luminal enlargement with a residual stenosis of less than 50%) was achieved in 152 lesions (92%); clinical success (technical success and no in-hospital death, Q-wave myocardial infarction or coronary bypass surgery) was achieved in 143 patients (91%). Adjunctive balloon angioplasty was used in 41 patients. DCA was successful less often in group 1 than in group 2 (86 vs 97%; p = 0.038). A major complication occurred in 7% of patients; in-hospital death, Q-wave myocardial infarction and emergency coronary bypass surgery occurred in 3, 1 and 4% of patients, respectively. Major complications were more frequent in group 1 than in group 2 (10 vs 1; p = 0.02). During a follow-up period of 14 +/- 8 months, no difference between the groups was found in the incidence of late death (4%), Q-wave myocardial infarction (1%), recurrent severe angina (29%), bypass surgery (15%) or repeat interventional procedure of the same vascular segment (24%). Vein graft and restenosis lesions tended to have greater success and fewer complications. Angiographic restenosis (increase of greater than or equal to 30% in stenosis severity by visual assessment) occurred in 62% of patients and 58% of lesions with successful DCA, and was similar in the 2 groups; a tendency toward higher restenosis rates was seen in patients with vein graft DCA.(ABSTRACT TRUNCATED AT 250 WORDS)