The effect of a venous filter on the embolic load during medullary canal pressurization: a canine study.

BACKGROUND: Acute intramedullary stabilization of femoral shaft fractures in multiply injured patients is controversial. Intravasation of medullary fat during canal pressurization has been suspected to trigger adult respiratory distress syndrome. The goal of the present study was to evaluate the effect, on the lungs, of a filter placed into the ipsilateral common iliac vein during medullary canal pressurization in a canine model. METHODS: With use of an established model of fat embolization, twelve mongrel dogs were randomized into two groups. In six dogs, a special filter was inserted percutaneously into the left common iliac vein while the dogs were under general anesthesia. In all dogs, the left femur and tibia were then pressurized by injection of bone cement and insertion of intramedullary rods. Hemodynamic measurements and echocardiographic images were recorded throughout the experiment. After one hour, the animals were killed and the lungs were harvested for histomorphometric analysis. RESULTS: Without the filter, the mean pulmonary artery pressure increased by 11.8 +/- 2.1 mm Hg (p < 0.001). With the filter, the mean pulmonary artery pressure increased by only 2.2 +/- 0.8 mm Hg (p < 0.02). Without the filter, there was a significant increase in the index of pulmonary vascular resistance as compared with the baseline value (p < 0.05). With the filter, there was no such increase. Histomorphometric analysis demonstrated that the presence of the filter reduced the absolute area of embolization and the volume percentages of lung and pulmonary vasculature embolized. CONCLUSIONS: In this canine experiment, temporary placement of a venous filter prior to medullary canal pressurization reduced the embolic load and minimized its hemodynamic effects.

A randomized trial comparing primary angioplasty with a strategy of short-acting thrombolysis and immediate planned rescue angioplasty in acute myocardial infarction: the PACT trial. PACT investigators. Plasminogen-activator Angioplasty Compatibility Trial.

OBJECTIVES: The study evaluated the efficacy and safety of a short-acting reduced-dose fibrinolytic regimen to promote early infarct-related artery (IRA) patency during the inherent delay experienced by infarct patients referred for angioplasty as the principal recanalization modality. BACKGROUND: Previous approaches using long-acting, full-dose thrombolytic infusions rarely showed benefit, but they did increase adverse event rates. METHODS: Following aspirin and heparin, 606 patients were randomized to a 50-mg bolus of recombinant tissue-type plasminogen activator (rt-PA) (alpha half-life 4.5 min) or to placebo followed by immediate angiography with angioplasty if needed. The end points included patency rates on catheterization laboratory (cath lab) arrival, technical results when PTCA (percutaneous transluminal coronary angioplasty) was performed, complication rates, and left ventricular (LV) function by treatment assignment and time to restored patency following angioplasty. RESULTS: Patency on cath lab arrival was 61% with rt-PA (28% Thrombolysis in Myocardial Infarction trial [TIMI]-2, 33% TIMI-3), and 34% with placebo (19% TIMI-2, 15% TIMI-3) (p = 0.001). Rescue and primary PTCA restored TIMI-3 in closed arteries equally (77%, 79%). No differences were observed in stroke or major bleeding. Left ventricular function was similar in both treatment groups, but convalescent ejection fraction (EF) was highest with a patent IRA (TIMI-3) on cath lab arrival (62.4%) or when produced by angioplasty within an hour of bolus (62.5%). However, in 88% of angioplasties, the delay exceeded 1 h: convalescent EF 57.3%. CONCLUSIONS: Tailored thrombolytic regimens compatible with subsequent interventions lead to more frequent early recanalization (before cath arrival), which facilitates greater LV function preservation with no augmentation of adverse events.

'Primary intention' intracoronary stenting guided by angiography alone: a safe approach.

OBJECTIVE: To examine the outcome of intracoronary stent placement by 'primary intention', guided by angiography alone, and without the use of postprocedural anticoagulation. DESIGN: Prospective, observational study. SETTING: Canadian university teaching hospital. PATIENTS: Patients (n=559) undergoing urgent or elective percutaneous revascularization procedures (n=616) in whom a preprocedural decision to employ coronary stent placement was made. Emergency and bailout stent procedures were excluded. INTERVENTION: Stents were delivered at high pressure (1616 to 1818 kPa) on balloons matched to the proximal reference segment diameter. Adequacy of stent deployment was judged by angiographic criteria alone. Postprocedural medication included acetylsalicylic acid and ticlopidine. Quantitative coronary angiographic analysis was independently performed. Acute procedural outcomes were prospectively collected. Patients were followed for one year. RESULTS: All but one patient had a successful angiographic result. Periprocedural death (0.3%), Q wave myocardial infarction (MI) (0%), non-Q MI (1.6%) and stent thrombosis (0.6%) were uncommon events. At one year, 96% of patients were alive and free of MI, while 12% of patients required repeat target lesion revascularization. CONCLUSION: A primary intention strategy of intracoronary stenting, guided by angiography alone, is a safe and effective approach to percutaneous coronary revascularization.

Antiarrhythmic drug effects on QT interval dispersion in patients undergoing electropharmacologic testing for ventricular tachycardia and fibrillation.

The effects of antiarrhythmic drugs on QT interval dispersion as a predictor of antiarrhythmic drug therapy has not been rigorously assessed. This study was performed to determine whether the effects of antiarrhythmic drugs on QT interval dispersion predict antiarrhythmic drug response in patients undergoing electropharmacologic testing for ventricular tachycardiarrythmias. Precordial QT intervals and QT interval dispersions were measured at baseline and during steady-state antiarrhythmic drug therapy in 72 consecutive patients with documented coronary artery disease and remote myocardial infarction presenting with spontaneous sustained ventricular tachyarrhythmias who underwent electropharmacologic studies to assess arrhythmia suppression. QT interval dispersion was similar at baseline in drug responders (42 +/- 21 ms) and drug nonresponders (46 +/- 21 ms), whereas during antiarrhythmic therapy QT interval dispersion was shorter in drug responders (33 +/- 15 ms) than in drug nonresponders (55 +/- 29 ms, p <0.001). QT interval dispersion was shorter in 7 drug responders during their effective drug trials (27 +/- 14 ms) than during their ineffective drug trials (47 +/- 24 ms, n = 9, p <0.05). QT dispersion < or = 50 ms (p <0.002) and a patent infarct-related artery (p <0.003) were independent predictors of antiarrhythmic therapy. The positive and negative predictive value of QT interval dispersion during drug therapy to predict a successful drug response was 32% and 96%, respectively. QT interval dispersion predicted the outcome of electropharmacologic studies independent of infarct-related artery patency. QT interval dispersion >50 ms during drug therapy was associated with ineffective drug therapy.

Clinical outcomes of patients more than one year following randomization in the Canadian Coronary Atherectomy Trial (CCAT).

BACKGROUND: The Canadian Coronary Atherectomy Trial (CCAT) assessed, in a randomized comparison, the clinical and angiographic outcomes following atherectomy with those following balloon angioplasty for the treatment of de novo lesions in the proximal one-third of the left anterior descending artery (LAD). Although the procedural success rate was somewhat higher and the postprocedure lumen larger in patients treated with atherectomy, lumen dimensions, restenosis rates and clinical outcomes were similar in the two groups at six months. To determine whether late differences emerged between the groups, clinical follow-up was obtained at a median of 18 (range 10 to 31) months after randomization. METHODS AND RESULTS: Patients were contacted monthly by telephone for the first six months. Subsequent follow-up information was obtained in 272 (99%) of the 274 randomized patients via a clinic visit or telephone interview with the patient and/or a relative. Additional information was obtained from the referring physician as required. There were no differences in adverse events between the two groups during follow-up. In patients randomized to atherectomy compared with balloon angioplasty, death occurred in 1.5% versus 2.2% (cardiac death 0.7% versus 0.7%); myocardial infarction in 5.1% versus 5.9% (Q wave 1.5% versus 1.5%); coronary bypass surgery in 13.1% versus 12.6%; and repeat target lesion intervention in 22.6% versus 21.5%. Persistent or recurrent Canadian Cardiovascular Society class III/IV angina not treated by a further intervention was present in 1.5% versus 2.2%. The combined end-point of death or nonfatal myocardial infarction occurred in nine (6.6%) versus 11 (8.1%) patients and any adverse cardiac event in 50 (36.5%) versus 53 (39.3%). Multivariate logistic regression indicated that unstable angina, reference vessel size and preprocedure minimum lumen diameter were the only variables independently associated with adverse events. CONCLUSIONS: The initial choice of directional atherectomy or balloon angioplasty had no impact on clinical outcome over a period of 18 months in this patient population. With either technique, just over 60% of patients with proximal LAD disease experienced sustained symptomatic improvement without an adverse event following a single procedure, and 80% achieved this status following a repeat percutaneous intervention.

Relation of pacing-induced coronary resistance vessel dilation to total serum cholesterol and heart rate-blood pressure product.

Coronary risk factors adversely affect coronary resistance vessel dilation to acetylcholine, but little is known about the effect of risk factors on coronary blood flow (CBF) responses to physiologic stimuli. CBF was derived from Doppler flow velocity (0.018-inch Doppler wire) and coronary diameter (quantitative angiography) in response to rapid atrial pacing in 50 patients (mean age 52 +/- 12 years). Patients were prospectively divided into 3 groups based on their angiograms: group 1 (n = 17), normal coronary arteries; group 2 (n = 18), 1-vessel coronary artery disease (CAD) with a smooth study artery; group 3 (n = 15), 1-vessel CAD and an irregular study artery (<20% stenosis). Pacing produced a significant increase in CBF compared with baseline in groups 1 and 2 (34 +/- 40%, 42 +/- 35%, p < 0.0001), respectively, but not in group 3 (21 +/- 33%), but there was no difference in the pacing response among the 3 groups. The increase in CBF to pacing was inversely related to serum cholesterol (p = 0.01) and triglycerides (p = 0.06) and directly related to the increase in heart rate-blood pressure product (p = 0.007). By multivariate analysis, total cholesterol and the increase in double product were the only factors related to the increase in CBF. Increases in CBF to atrial pacing are inversely related to serum total cholesterol and are not related to the angiographic presence of atherosclerosis in patients with mild CAD.

Effect of coronary angioplasty on precordial QT dispersion.

Dispersion of the QT interval is a measure of inhomogeneity of ventricular repolarization. Because ischemia is associated with regional abnormalities of conduction and repolarization, we hypothesized that the surface electrocardiographic interval dispersion would increase in patients with symptomatic coronary artery disease in the absence of myocardial infarction and that successful revascularization would reduce QT interval dispersion. Thirty-seven consecutive patients with ischemia due to 1-vessel coronary artery disease without prior myocardial infarction who underwent percutaneous transluminal coronary angioplasty (PTCA) were evaluated. Standard 12-lead electrocardiograms were performed 24 hours before, 24 hours after, and late (>2 months) after PTCA. Precordial QT interval dispersions were determined from differences in the maximum and minimum corrected QT intervals. Mean QT interval dispersion before PTCA was 60 +/- 9 ms, immediately after PTCA 23 +/- 14 ms (p <0.001), and late after PTCA 29 +/- 18 ms (p <0.001 vs before PTCA). The shortest precordial QT interval increased immediately after PTCA (367 +/- 40 vs 391 +/- 39 ms; p <0.02) and then remained stable late after PTCA (376 +/- 36 ms, p = NS vs immediately after PTCA). Symptomatic recurrent ischemia in 8 patients with documented restenosis increased QT interval dispersion (56 +/- 15 ms [p <0.01] vs 25 +/- 14 ms immediately after PTCA), which decreased again after successful repeat PTCA (22 +/- 13 ms [p <0.01] vs before the second PTCA). QT interval dispersion decreases after successful coronary artery revascularization and increases with restenosis. Therefore, QT interval dispersion may be a marker of recurrent ischemia due to restenosis after PTCA.

A comparison of directional atherectomy with balloon angioplasty for lesions of the left anterior descending coronary artery.

BACKGROUND: Restenosis is a major limitation of coronary angioplasty. Directional coronary atherectomy was developed with the expectation that it would provide better results than angioplasty, including a lower rate of restenosis. We undertook a randomized, multicenter trial to compare the rates of restenosis for atherectomy and angioplasty when used to treat lesions of the proximal left anterior descending coronary artery. METHODS: Of 274 patients referred for first-time, non-surgical revascularization of lesions of the proximal left anterior descending coronary artery, 138 were randomly assigned to undergo atherectomy and 136 to undergo angioplasty; 257 of 265 eligible patients (97 percent) underwent follow-up angiography at a median of 5.9 months. Computer-assisted quantitative measurements of luminal dimensions were determined from the angiograms obtained before and immediately after the procedure and at follow-up. The primary end point of restenosis was defined as stenosis of more than 50 percent of the vessel's diameter at follow-up. RESULTS: Quantitative analysis showed that the procedural success rate was higher in patients who underwent atherectomy than in those who had angioplasty (94 percent vs. 88 percent, P = 0.061); there was no significant difference in the frequency of major in-hospital complications (5 percent vs. 6 percent). At follow-up, the rate of restenosis was 46 percent after atherectomy and 43 percent after angioplasty (P = 0.71). Despite a larger initial gain in the minimal luminal diameter with atherectomy (mean [+/- SD], 1.45 +/- 0.47 vs. 1.16 +/- 0.44 mm; P < 0.001), there was a larger late loss (0.79 +/- 0.61 vs. 0.47 +/- 0.64 mm; P < 0.001), resulting in a similar minimal luminal diameter in the two groups at follow-up (1.55 +/- 0.60 vs. 1.61 +/- 0.68, P = 0.44). The clinical outcomes at six months were not significantly different between the two groups. CONCLUSIONS: The role of atherectomy in percutaneous coronary revascularization remains to be fully defined. However, as compared with angioplasty, atherectomy did not result in better late angiographic or clinical outcomes in patients with lesions of the proximal left anterior descending coronary artery.

Infarct artery patency predicts outcome of serial electropharmacological studies in patients with malignant ventricular tachyarrhythmias.

BACKGROUND: Surviving myocardial cells near the infarct border zone form the arrhythmogenic substrate for sustained ventricular tachycardia (VT) in humans. Infarct-related artery (IRA) patency may modulate the electrophysiological function of this arrhythmogenic substrate and its response to antiarrhythmic drug therapy. We postulated that effective antiarrhythmic drug therapy selected during serial electrophysiological studies in patients with VT after a myocardial infarction would be identified more frequently when the IRA is patent than when chronically occluded. METHODS AND RESULTS: Consecutive patients (n = 64) with documented coronary artery disease and remote myocardial infarction presenting with spontaneous sustained VT or ventricular fibrillation (VF) were studied. These patients underwent 4 +/- 2 electropharmacological studies identifying effective antiarrhythmic drug therapy in 16 (25%) patients. Drug responders did not differ significantly from nonresponders in demographic, electrocardiographic, angiographic, or hemodynamic measurements. A patent IRA was associated with antiarrhythmic drug response significantly more frequently than was an occluded IRA (45% versus 9%, p = 0.001). Patency of the IRA was the only independent predictor of response to antiarrhythmic drug therapy in this study population. The sensitivity and specificity of using a patent IRA to predict successful drug testing were 81% and 67%, respectively. CONCLUSIONS: The outcome of electropharmacological studies was predicted by the patency of the IRA. A patent IRA was associated with a greater probability of finding effective drug therapy.

Left main coronary artery dissection during cardiac catheterization.

A 70-year-old man with a downward sloping origin of the left main coronary artery developed left main dissection at coronary angiography and died despite emergency coronary by-pass surgery. Autopsy showed that the left main coronary artery had an acute angle take off and dissection had originated at the junction of the superior wall of the left main and the aorta. The combination of left main stenosis secondary to dissection and severe right coronary atherosclerosis had caused circumferential subendocardial left ventricular infarction. The left main coronary artery had mild atherosclerosis and lacked cystic medial necrosis. An angulated left main coronary artery may be a risk factor for dissection at angiography.

The right and left ventricular intracavitary and transmural pressure-strain relationships.

The magnitude of pericardial pressure and therefore the shape of the right ventricular end-diastolic transmural pressure-volume relationship remains controversial. To investigate ventricular compliance, eight dogs anesthetized with fentanyl were instrumented as follows. Right and left ventricular intracavitary pressures were measured with micromanometer-tipped catheters. Right and left ventricular free wall segment lengths were measured by sonomicrometry. Pericardial pressure was measured over the right and left ventricles by means of flat liquid-containing balloon transducers, and transmural pressures were calculated as the difference between intracavitary and pericardial pressures. After defining the pressure-segment length relationship by vena caval constriction followed by release and blood transfusion, the pericardium and chest were opened widely and the cardiac volume manipulation was repeated; this allowed direct measurement of transmural right ventricular end-diastolic pressure for each level of strain recorded with the chest and pericardium closed. When intracavitary right or left ventricular end-diastolic pressure was raised from zero to 20 mm Hg, the respective transmural pressures increased from 0.2 +/- 0.6 (SD) mm Hg to 2.5 +/- 1.8 mm Hg and from 0.3 +/- 0.7 mm Hg to 6.0 +/- 2.5 mm Hg. Ventricular segmental strain increased by 7.0 +/- 0.8% and 6.0 +/- 0.2%, respectively. No statistically significant differences were found between right ventricular calculated (intracavitary minus pericardial pressure) and measured (open pericardium, open chest) transmural pressures at a given strain, thereby confirming the accuracy of our pericardial pressure measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Rescue angioplasty during myocardial infarction has a beneficial effect on mortality: a tenable hypothesis.

HYPOTHESIS: Rescue percutaneous transluminal coronary angioplasty (PTCA) reduces mortality during myocardial infarction. OBJECTIVE: To determine if PTCA after failed thrombolytic therapy results in reduced mortality. DESIGN: Twenty-eight patients with a persistently occluded infarct artery following thrombolytic therapy more than 3 h after symptom onset were randomized to rescue PTCA (n = 16) or conservative treatment (n = 12) as part of a prospective randomized trial of reperfusion therapy during myocardial infarction in 184 patients. Hospital mortality was assessed in these groups as well as in the 177 patients with known infarct artery status after initial attempts at reperfusion. MAIN RESULTS: There was one death among the 16 patients in the rescue PTCA group versus four deaths in the 12 patients treated conservatively (P = 0.13). Moreover, the death in the rescue PTCA group occurred in one of three patients in whom the procedure failed. Mortality in the entire study group was 10.3% (19 of 184); 4.2% (six of 142) in patients in whom patency was achieved after thrombolysis and/or PTCA and 34.3% (12 of 35) in those in whom reperfusion was not achieved (P less than 0.001). In patients with anterior myocardial infarction, mortality was 6.7% (four of 60) in those with reperfusion and 47.1% (eight of 17) in those with a persistently occluded artery (P less than 0.001). In patients with inferior myocardial infarction, 2.4% (two of 82) with reperfusion and 22.2% (four of 18) with a persistently occluded artery died (P less than 0.01). CONCLUSIONS: Although the number of patients in the randomized groups was small, the trend toward a lower mortality after rescue PTCA supports the hypothesis that rescue PTCA may be beneficial. The mortality results in relation to presence or absence of reperfusion from the entire study population underscores the importance of achieving patency during myocardial infarction.

Experimental instrumentation and left ventricular pressure-strain relationship.

Pericardial pressure measurement with a balloon transducer requires opening and reapproximating the pericardium. If this instrumentation significantly compromises pericardial volume, the heart may be constrained, exaggerating the magnitude of pericardial pressure and thus altering the left ventricular end-diastolic pressure-volume relationship. In open-chest dogs, we studied the effects of opening the pericardium, inserting a pericardial balloon transducer and myocardial sonomicrometer crystals, and reapproximating the pericardium on the left ventricular end-diastolic pressure-strain relationship (LVEDPSR). After a thoracotomy, sonomicrometer crystals were inserted through small holes (less than 3 mm) in the pericardium to measure LV segment length. A micromanometer with a reference lumen was used to measure LV pressure. LVEDPSRs were recorded in the following situations: 1) before the pericardium was opened (but after the crystals were inserted); 2) after the pericardium was opened, the heart was instrumented (4 pairs of crystals and 1 balloon), and the pericardium was reapproximated with interrupted sutures; and 3) after the pericardium was removed. For each dog, a cubic regression equation was fitted to the data obtained before opening the pericardium, and the 95% confidence intervals for the individual data points were determined. In each case, the LVEDPSR obtained after instrumentation was similar to the LVEDPSR described before opening the pericardium. Furthermore, data obtained after instrumentation were uniformly located within the confidence intervals of the LVEDPSR obtained before opening the pericardium and instrumenting the heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between flow grade after thrombolytic therapy and the effect of angioplasty on left ventricular function: a prospective randomized trial.

Recent intervention trials during myocardial infarction demonstrated no benefit from emergency angioplasty after thrombolytic therapy when compared with either delayed percutaneous transluminal coronary angioplasty (PTCA) or a conservative strategy. However, it is possible that subgroups of patients may benefit from early intervention with angioplasty. We performed a prospective randomized trial in patients with a patent infarct-related artery after thrombolytic therapy to determine whether initial flow grade is related to infarct-zone function and whether patients with ineffective reperfusion (greater than 90% stenosis or Thrombolysis in Myocardial Infarction [TIMI] flow less than or equal to 2) might benefit from immediate PTCA. Thrombolytic therapy was administered to 170 patients at a mean of 2.1 +/- 0.5 hours after onset of myocardial infarction. A patent infarct-related artery that was suitable for angioplasty was present in 89 patients who comprised the study group; after randomization, 47 of 50 patients with a patent infarct-related artery had successful emergency PTCA 3.8 +/- 1.5 hours after onset of symptoms, and 39 were scheduled for delayed (18 to 48-hour) PTCA. Reocclusion occurred before the scheduled (delayed) procedure in eight patients (20.5%), and was symptomatic in six. Infarct-region function (by the centerline method) measured initially, before discharge, and at 4 months was similar in both groups; improvement was significant (p less than 0.001) at discharge when compared with initial values with no further change at 4 months. However, patients with ineffective reperfusion had greater hypokinesia initially (p less than 0.05) compared with those with effective reperfusion (less than or equal to 90% stenosis plus TIMI flow 3). Moreover, independent of the timing of PTCA, improvement was greater before discharge in patients with ineffective reperfusion (p less than 0.05) with a trend also evident at 4 months. Importantly, 42 of 51 patients (82%) with a residual lumen less than 0.4 mm after thrombolysis had some improvement in function at discharge; this compared with a previous study in which patients with a similar degree of stenosis (without PTCA) had no improvement. Moreover, reocclusion occurred before scheduled (delayed) PTCA in 37% of patients with greater than 90% stenosis compared with only 5% in those with less than or equal to 90% stenosis (p = 0.02). Thus flow grade is an important determinant of myocardial function in patients with a patent artery after thrombolytic therapy and is predictive both of improvement in wall motion after PTCA and early reocclusion.(ABSTRACT TRUNCATED AT 400 WORDS)