Influence of elastic recoil on restenosis after successful coronary angioplasty in unstable angina pectoris

The use of low molecular weight heparin to predict clinical outcome in patients with unstable angina that had undergone percutaneous coronary intervention

BACKGROUND

Antithrombotic therapy with heparin reduces the rate of ischemic events in patients with acute coronary syndrome. Low-molecular-weight heparin, given subcutaneously twice daily, has a more predictable anticoagulant effect than standard unfractionated heparin. Moreover, it is easier to administer and does not require monitoring.

METHODS

We prospectively analyzed 180 patients with unstable angina who had undergone percutaneous coronary intervention (PCI) between 1999 and 2001 at Chonnam National University Hospital and had received either 120 U/kg of dalteparin (Fragmin), administered subcutaneously twice daily (Group I; n = 90, 61.8 +/- 8.9 years, male 67.8%), or had received continuous intravenous unfractionated heparin (Group II; n = 90, 62.6 +/- 9.7 years, male 70.0%). During hospitalization and at 6 month after PCI, major adverse cardiac events such as acute myocardial infarction, target vessel revascularization, death, and restenosis were examined.

RESULTS

During hospitalization, the incidence of acute myocardial infarction, target vessel revascularization and death were not different between the two groups. At follow-up coronary angiography 6 months after PCI, the incidence of restenosis was lower in group I than in group II (Group I; 26/90, 28.8% vs. Group II; 32/90, 35.6%, p = 0.041) and the incidence of target vessel revascularization was lower in group I than in group II (Group I; 21/90, 23.3% vs. Group II; 27/90, 30.0%, p = 0.039). No difference was found in the rates of major and minor hemorrhages, ischemic strokes or thrombocytopenia between two groups. By multivariate analysis, the factors related to restenosis were lesion length, postprocedural minimal luminal diameter, CRP on admission, diabetes mellitus, the type of heparin, and stent use.

CONCLUSION

Dalteparin, a low molecular weight heparin, is superior to standard unfractionated heparin in terms of reducing the restenosis rate and target vessel revascularization without increasing bleeding complications.

Early changes in coronary flow physiology after balloon angioplasty or stenting: a 24-hour Doppler flow velocity study

To evaluate early changes in myocardial microcirculation after balloon or stent coronary angioplasty, we studied 57 patients undergoing coronary angioplasty with a Doppler-tipped guidewire, with (n = 26) or without stenting. Postprocedural quantitative coronary angiography and coronary flow velocity were measured after 10 min and 24 hr. As compared to stenting, no stenting was associated with a higher postprocedural stenosis rate (21% +/- 13% vs. 12% +/- 10%; P < 0.05), smaller coronary velocity reserve (CVR; 2.2 +/- 0.4 vs. 2.5 +/- 0.7; P = 0.04), and smaller relative CVR (0.8 +/- 0.2 vs. 1.1 +/- 0.3; P = 0.001). At 24 hr, CVR and relative CVR in the unstented group increased to the level in the stented group, mainly because of a decrease in basal average peak velocity (APV). Overall, there was a significant negative linear relation between CVR and APV variations during the 24-hr period. In the subgroups with persistent abnormalities, CVR variation was closely related to the basal APV/reference APV ratio. In conclusion, coronary reserve normalization can occur within 24 hr after coronary angioplasty and is closely dependent on postangioplasty APV. Myocardial distal resistances should be considered when interpreting postangioplasty CVR.

Intravascular ultrasonic comparisons of mechanisms of vasodilatation of cutting balloon angioplasty versus conventional balloon angioplasty

Intimal hyperplasia after balloon dilatation may be related to the severity of vascular injury, and cutting balloon angioplasty (CBA) may reduce vascular injury. The present study investigated the mechanism of vasodilation by CBA. Intravascular ultrasound examination was performed before and after intervention in 40 lesions treated with CBA and in 25 lesions treated with conventional balloon angioplasty. Intravascular ultrasound measurements included the vessel area, luminal area, and plaque area. Vessel expansion was evaluated as the ratio of the postprocedural vessel area to that before intervention. The vessel area was 13.9 +/- 3.2 and 14.8 +/- 3.2 mm(2) after CBA versus conventional angioplasty, respectively, whereas the luminal area was 5.5 +/- 1.2 versus 5.7 +/- 1.2 mm(2) and the plaque area was 8.5 +/- 2.7 versus 9.1 +/- 2.2 mm(2), respectively. The vessel area was smaller and the plaque area significantly smaller after CBA. Vessel expansion accounted for 45% of luminal enlargement, and plaque compression or shift accounted for 55% after CBA. After conventional angioplasty, vessel expansion accounted for 67%, and plaque compression or shift for 33% of luminal enlargement. The vessel expansion ratio was significantly smaller after CBA than after conventional angioplasty (1.05 vs 1.22, p <0.05). These findings suggest that the predominant mechanism of dilatation after CBA is plaque compression or shift rather than vessel expansion, unlike conventional angioplasty.

Mechanisms of angioplasty and stent restenosis: implications for design of rational therapy

Restenosis after angioplasty or stenting remains the major limitation of both procedures. A vast array of drug therapies has been used to prevent restenosis, but they have proven to be predominantly unsuccessful. Recent trends in drug therapy have attempted to refine the molecular and biological targets of therapy, based on the assumption that a single biological process or molecule is critical to restenosis. In contrast, both stenting and brachytherapy, which are highly nonspecific, can successfully reduce restenosis after angioplasty or stenting, respectively. This review examines the biology of both angioplasty and stent stenosis, focussing on human studies. We also review the landmark human trials that have definitively proven successful therapies, such as stenting and brachytherapy. We suggest that the successful trials of stenting and brachytherapy and the failure of other treatments have highlighted the shortcomings of conventional animal models of arterial intervention, and gaps in our knowledge of human disease. In contrast to arguments advocating gene therapy, these studies suggest that the most likely successful drug therapy will have a wide therapeutic range, targeting as many of the components or biological processes contributing to restenosis as possible.

In vivo assessment of stent recoil in normal porcine arteries: evaluation of contemporary stent designs

Acute stent recoil has been observed following balloon deflation in normal and diseased coronary arteries, and the magnitude varies by stent design. We sought to evaluate acute stent recoil in five new stents. Twenty-five stents (four Crown, five Nir Conformer Royale, five Crossflex, five SupraG, and six GFX) were implanted in six Yorkshire pigs. All stents were expanded using a noncompliant balloon (balloon:artery ratio 1.2:1.0). Continuous ultrasound imaging was performed during stepwise balloon inflation and deflation using a 0.018" imaging core. Maximum cross-section areas (CSA) and minimal luminal diameter (MLD) were measured at 12 atm and immediately following balloon deflation. Maximum stent CSA matched expected balloon CSA. Area and diameter recoil were calculated as 1 - (CSAdeflation/CSAmax) and 1 - (MLDdeflation/MLDmax), respectively. Upon deflation, all stents showed recoil from maximal CSA. Area recoil was significantly lower for slotted-tube stents than modular stents (12.6% +/- 1.6% vs. 23.2 +/- 3.5%; P < 0.05). In compliant, nonatherosclerotic porcine coronary arteries, acute stent recoil for the four slotted-tube designs ranged from 8.4% to 18.0% by area. The modular stent tested was associated with significantly greater acute recoil than the slotted-tube stents.

Early lumen diameter loss after percutaneous transluminal coronary angioplasty is related to coronary plaque burden: a role for viscous plaque properties in early lumen diameter loss

OBJECTIVES

We tested the hypothesis that lumen diameter loss within 1 h after percutaneous transluminal coronary angioplasty is related to plaque volume parameters.

BACKGROUND

Early lumen diameter loss after coronary balloon angioplasty may predict restenosis and may paradoxically decrease late lumen diameter loss. Viscous properties of the vessel wall, as would be determined by tissue volume and composition, may be involved in early lumen diameter loss.

METHODS

Early lumen diameter loss was measured with quantitative coronary angiography as the loss in lesion lumen diameter (significant loss 0.4 mm) occurring between 5 min and a median of 40 min after successful coronary balloon angioplasty in 68 patients. Thirty-nine patients were evaluated with intravascular ultrasound at the narrowest lumen cross-section of the dilated lesion, 29 patients formed a control group without intravascular ultrasound imaging. We tested the relation between intravascular ultrasound parameters and early lumen diameter loss.

RESULTS

Early lumen diameter loss of > or = 0.4 mm was present in eight patients (12%), decreasing lumen diameter from 2.26 +/- 0.36 mm to 1.73 +/- 0.43 mm. There was no difference in the frequency of early lumen diameter loss between the groups with or without intravascular ultrasound imaging. Univariate intravascular ultrasound determinants of early lumen diameter loss were media bounded area (p = 0.01), maximal plaque thickness (p = 0.02), eccentricity index (p = 0.03) and the presence of hard lesions (p = 0.02).

CONCLUSION

Early lumen diameter loss in the first hour after successful coronary balloon angioplasty occurs in a small proportion of patients. It is related to hard lesion type, maximal plaque thickness and eccentricity index, favoring a role for viscous plaque properties in early lumen diameter loss.

Intracoronary serum smooth muscle myosin heavy chain levels following PTCA may predict restenosis

Recently a novel biochemical method that uses an immunoassay to quantitate serum smooth muscle myosin heavy chain (SMMHC) levels was developed for diagnosis of aortic dissection.) The purpose of this study was to determine whether SMMHC released from the coronary arterial wall can be used to predict restenosis after percutaneous transluminal coronary angioplasty (PTCA). Fifty-two consecutive patients undergoing successful PTCA for single vessel disease were examined (40 men, 12 women, 63 +/- 8 years). Intracoronary blood samples were obtained distal to the lesion, and from the femoral artery after PTCA. In 10 patients, blood samples were taken immediately after the final balloon inflation, and 10 and 20 minutes after PTCA. SMMHC levels were measured by ELISA using SMMHC-specific monoclonal antibodies. Follow-up coronary angiography was performed 3 months after PTCA. Intracoronary serum SMMHC levels were significantly higher than those obtained from the femoral artery (10.6 +/- 1.5 vs 2.1 +/- 0.1 ng / ml, p < or = 0.001). Of 40 patients without apparent dissection, the 23 patients who did not develop restenosis in the follow-up study were found to have had higher levels of intracoronary SMMHC levels immediately after PTCA compared to the 17 patients with restenosis (15.2 +/- 2.9 vs 7.1 +/- 1.2 ng /ml, p < or = 0.05). We suggest that elevated intracoronary SMMHC levels after PTCA may reflect the extent of injury to the arterial wall. Intracoronary SMMHC may be a possible biochemical marker for the prediction of restenosis.

Pharmacogenetic analysis of the effect of angiotensin-converting enzyme inhibitor on restenosis after percutaneous transluminal coronary angioplasty

Angiotensin-converting enzyme (ACE) inhibitors are reported to prevent neointimal formation after balloon injury in animal models, but in most prospective studies in humans, ACE inhibitors failed to prevent restenosis after percutaneous transluminal coronary angioplasty (PTCA). The ACE genotype assigned by an insertion/deletion (I/D) polymorphism is known to affect the potency of ACE inhibitors in several renal diseases. The authors attempted to clarify whether the effect of ACE inhibitors on restenosis might be modified by the ACE genotype. A total of 126 patients was randomly and prospectively assigned to the control group and the imidapril group. In the imidapril group, patients received 5 mg imidapril daily, starting 1 day before PTCA and continuing for 3 to 6 months. Forty-six control (65 vessels) and 32 imidapril patients (43 vessels) completed the study. The minimal lumen diameter before and after the procedure did not differ significantly among the groups with the three genotypes (II, ID, and DD) in both the control and imidapril groups. Late luminal loss during the follow-up period was not related to the ACE genotype in the control group but was significantly related in the imidapril group (II, 0.63+/- 0.19 mm; ID + DD, 1.12+/-0.14 mm, p<0.05). Furthermore, in the II genotype, imidapril significantly reduced late loss and restenosis rate as defined by most of the frequently used definitions. In conclusion the ACE I/D polymorphism may influence the effect of ACE inhibitors in preventing restenosis after PTCA.

Adjunctive stent implantation following directional coronary atherectomy in patients with coronary artery disease

OBJECTIVES

This prospective case-control study evaluated the acute and long-term results of stent implantation preceded by debulking of the plaque by means of directional coronary atherectomy.

BACKGROUND

In comparison with balloon angioplasty, intracoronary stenting produces a larger luminal diameter, maintains artery patency and reduces the incidence of restenosis. Optimal stent deployment is a pivotal factor for achieving the best results, but the bulk of the atherosclerotic plaque opposes stent expansion and may limit the success of the procedure. Debulking of the plaque may provide a better milieu for optimal stent deployment.

METHODS

Directional coronary atherectomy followed by a single Palmaz-Schatz stent implantation was attempted in 100 patients. The successes, complications and angiographic results of the combined procedure were evaluated both acutely and during follow-up. Matched patients undergoing successful Palmaz-Schatz stent implantation alone during the same period served as controls.

RESULTS

Atherectomy followed by stent implantation was performed in 94 patients with 98 lesions; periprocedural complications were observed in four cases. The stenosis diameter decreased from 76+/-9% at baseline to 30+/-13% after atherectomy (p < 0.0001), and 5+/-9% after stent implantation (p < 0.0001); it increased to 27+/-15% at 6-month angiography (p < 0.0001). During the 14+/-10 months of follow-up, none of the patients died or experienced myocardial infarction, but three patients underwent target lesion revascularization. The patients undergoing stent implantation alone achieved smaller acute gains, tended to have a higher late lumen loss, had a higher restenosis rate (30.5% vs. 6.8%, p < 0.0001) and showed a greater incidence of clinical events during follow-up (p < 0.0001).

CONCLUSIONS

Debulking atherosclerotic lesions by means of directional coronary atherectomy before stent implantation is a safe procedure with a high success rate and a low incidence of restenosis at follow-up.

Exaggerated luminal loss a few minutes after successful percutaneous transluminal coronary angioplasty in patients with recent myocardial infarction compared with stable angina: an intracoronary ultrasound study

This study investigates the mechanisms of exaggerated acute luminal loss after successful coronary angioplasty in patients with recent myocardial infarction compared with stable angina by angiography and intracoronary ultrasound (ICUS). We studied 15 consecutive patients (group 1) who, after a successful thrombolysis for myocardial infarction, underwent delayed (8 +/- 2 days after the myocardial infarction) successful balloon coronary angioplasty. Group 1 patients were individually matched with 15 stable angina patients (group 2). The percentage of stenosis and acute luminal loss were measured by quantitative coronary analysis. The ultrasound characteristics of lumen pathology were described as soft, hard, calcified, eccentric, concentric, thrombotic, and dissection lesions. Matching by stenosis location, reference diameter, sex, and age resulted in 2 comparable groups of 15 lesions with identical baseline characteristics. Immediately after percutaneous transluminal coronary angioplasty (PTCA), the minimal luminal diameter increased from 0.5 +/- 0.3 mm to 2.4 +/- 0.3 mm and from 0.5 +/- 0.2 mm to 2.4 +/- 0.3 mm in groups 1 and 2, respectively. Similar balloon sizes were used in both groups. The acute luminal loss (the difference between the maximal dilated balloon diameter and the minimal luminal diameter) immediately after PTCA was 0.4 +/- 0.2 mm and 0.3 +/- 0.3 mm (14 +/- 8% and 10 +/- 11% of balloon size) (P = not significant [NS]) in groups 1 and 2, respectively. After ICUS (mean 24 min after the last balloon deflation), the acute luminal loss was 0.9 +/- 0.3 mm and 0.5 +/- 0.4 mm (29 +/- 11% and 17 +/- 8% of balloon size) (P = 0.01) in groups 1 and 2, respectively. There was a significantly higher prevalence of intracoronary thrombus formation as detected by ICUS in group 1 compared with group 2 (80% vs. 20%; P < 0.001). In matched groups of successfully treated coronary angioplasty, patients with recent myocardial infarction had a similar magnitude of acute gained luminal loss immediately after the procedure. However, an exaggerated luminal loss a few minutes after the last balloon deflation in patients with recent myocardial infarction was noted because of mural thrombus formation compared with patients with stable angina.

Incidence and treatment of elastic recoil occurring in the 15 minutes following successful percutaneous transluminal coronary angioplasty

This study was performed (1) to assess the incidence and magnitude of elastic recoil occurring within 15 minutes of successful coronary angioplasty, and (2) to determine the effect of subsequent additional balloon inflations on coronary luminal diameter in patients displaying substantial recoil. The coronary angiograms of 50 consecutive patients who underwent a successful percutaneous transluminal coronary angioplasty were analyzed using computer-assisted quantitative analysis. The patients were divided into 2 groups based on the magnitude of early elastic recoil following angioplasty: those with < or = 10% (group I, n = 30) and those with > 10% (group II, n = 20) loss of minimal luminal diameter as assessed by comparing the angiogram obtained immediately after successful angioplasty with that obtained 15 minutes later. The 2 groups were similar in clinical, angiographic, and procedural characteristics. Of the 20 group II subjects, 18 (90%) underwent repeat balloon dilatations, and 2 patients (10%) had no further intervention. After additional balloon inflations were performed in these 18 patients, 16 (90%) had a final result with < 10% loss of minimal luminal diameter 15 minutes later. In conclusion, elastic recoil 15 minutes after apparently successful percutaneous transluminal coronary angioplasty is frequent, occurring in approximately 40% of patients, and is attenuated in 90% of subjects with additional balloon inflations. The resultant larger lumen diameter may exert a salutary effect on long-term outcome.

Mechanics of porcine coronary arteries ex vivo employing impedance planimetry: a new intravascular technique

Our objective was to evaluate methodological aspects of impedance planimetry, a new balloon catheter-based technique, for the investigation of coronary artery mechanical wall properties. We used a four ring-electrode electrical impedance measuring system that was located inside a balloon. Two of the electrodes were used for excitation and connected to a generator producing a constant alternating current of 250 mA at 5 kHz. The other two electrodes for detection were placed midway between the excitation electrodes. The balloon was distended with electrically conducting fluid through an infusion channel. The vessel cross-sectional area (CSA) was measured according to the field gradient principle by measuring the impedance of the fluid inside the balloon. Impedance planimetry was applied in the three major branches of the coronary arteries of seven extracted porcine hearts to assess luminal CSAs in response to internal pressurization. The biomechanical wall properties were evaluated by computing the strain [(r - r0) x r0(-1), where r is the vessels inner radius computed as (CSA x pi-1)1/2 and r0 is the radius of the vessel at a minimal distension pressure], the tension [(r x dP), where dP is the transmural pressure difference], and the pressure elastic modulus (delta P x r x delta r-1). We found that in vitro testing demonstrated that impedance planimetry was accurate and reproducible. The technique has controllable sources of error. Measurements were performed with consecutively increasing pressures in the range 1-25 kPa (8-188 mmHg, 0.01-0.25 atm). The CSAs increased nonlinearly and were significantly larger in the left anterior descendent coronary artery (LAD) (1 kPa, mean 5.0 mm2; 25 kPa, mean 21.8 mm2) than in both the left circumflex (Cx) (4.5-16.0 mm2) and the right coronary artery (RCA) (2.8-15.6 mm2) (analysis of variance, P < 0.001 for both). The circumferential wall tension-strain relation showed exponential behavior. For a given strain, tension values for LAD were significantly lower than those of Cx (P < 0.01). The pressure elastic modulus-strain relation also was exponential, and values for Cx were significantly lower than values for LAD (P < 0.001) and RCA (P < 0.05). Impedance planimetry was applied to the study of coronary artery biomechanics ex vivo. The LAD had the largest CSA, and the Cx was the least compliant. Methodological aspects of an in vivo introduction of the method require additional evaluation.