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Left Ventricular Function One Year
after Coronary Stenting

Izurieta, Hernán; Guzmán, Edwin; Ibarra, Rita

Servicio de Hemodinámica. Hospital Carlos Andrade Marín
Quito - Ecuador

SUMMARY
Introduction: Coronary revascularization with stents is associated with symptomatic improvement of patients and over the time may allow the restoration of left ventricular function with a significant impact on survival.
Objectives: This study was made to show the effect of coronary stenting in global and regional left ventricular function, one year after the implantation.
Materials and Methods: We designed an autocontrolled clinical trial that included 40 consecutive patients (37 male, 3 female) submitted to one or more coronary revascularizations with stents, and angiografically controlled after one year. Global ejection fraction (EF) was determined in the 30° right anterior oblique view (RAO30) of the left ventriculograms, before the implantation and a year after. In those patients with revascularization of the left anterior descending artery (ADA) we analyzed the regional longitudinal shortening (RLS) with the centerline method, of the 4 anterior segments supplied by this artery in the RAO30, before and after the procedure.
Results: Forty-nine arteries were successfully revascularizated (1,22±0,42 arteries/patient). All of them were angiografically controlled 14,39±4,77 months after; 71% were permeable, the EF before the implantation was 54,87%±13,48 (IC 95% 50,9-58,7) and after 56,52%±16,11 (IC 95% 51,8-61,1), p = 0,25. There were 24 ADA stented. The Table 1 shows the RLS measured in the 4 ADA areas before and 13,5±3,05 months after the stent implantation.

Table 1: % RLS in ADA Territory

Conclusion: After a year, coronary revascularization with stents produced a trend toward improvement of global left ventricular function. The RLS measured in the ADA territory also shows a significant improvement of the wall motion in a great part of the treated zone. This restoration of the left ventricular function may translate in better survival of patients, a fact that is consequent with the open artery hypothesis.

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INTRODUCTION
   The implantation of tubular intracoronary prosthesis (stents) has demonstrated to be an effective method of myocardial revascularization in order to alleviate the ischaemia. Technological improvements in the design of prosthesis have permitted to treat a greater number of patients, including those with complex lesions, multiple arteries, small vessels, venous grafts and subgroups with greater risk like ancients, those with severe left ventricular dysfunction, and others. Today, the use of stents is considered a valid alternative to surgical coronary bypass. Whichever the elected technique, myocardial revascularization pretends, on one hand, the symptomatic relief of patients with coronary artery disease and, for another, the survival improvement. Deterioration of left ventricular function is considered a predictor of poor survival and, in this sense, surgical revascularization has been especially beneficial in the subgroup with low ejection fraction (EF). Then, it is logic to suppose that restoration of flow by other techniques such as stenting may help to maintain or improve the regional and global left ventricular function.

   The present study was performed in order to demonstrate the effect of the coronary stenting in global and regional left ventricular function one year after implantation.

MATERIALS AND METHODS
   This is a prospective, longitudinal, autocontrolled clinical trial, for which consecutive patients with indication of stenting because of coronary artery disease, referred to the catheterization laboratory of the Carlos Andrade Marín Hospital between October 1996 and September 1999 were selected and, one year later, in the same service, were angiographically controlled. Previous the stenting procedure the patients were submitted to a diagnostic coronary angiography searching the lesions to be treated and to a left ventriculogram including a 30° right anterior oblique projection (RAO30). Demographic characteristics of the group were measured and registered, also the type of stent elected by the interventionist, the revascularizated artery that was categorized between: anterior descending (ADA), circumflex (CX), right coronary (RD) and others, the presence of recent myocardial infarct that was defined as the occurrence of this event in the fifteen precedent days to the diagnostic coronary angiography. The control angiography was performed previous the patient consent and also included a coronary study and a RAO30 left ventriculogram for analysis of the left ventricular function. The presence of restenosis, defined as any lesion > 50% in the revascularizated segment or any new lesion > 50% of the revascularizated artery was determined; total occlusions were also registered. The time between the implantation and control was measured in months. The patients were excluded if by any reason the left ventriculogram was omitted in one of the studies, those with any film with images not suitable for the left ventricular function analysis, for example too much arrhythmia and if, in spite of having programmed a stent placement, they were finally subjected to balloon angioplasty.

   The global left ventricular function was evaluated determining the EF. This measure was carried out in the in RAO30 projected in a Tagarno 35CX projector. A single investigator, blinded about the origin of frames, traced manually the end-systolic and end-diastolic contours. Then they were introduced in a computer to be analyzed with the Angiographic Ventricular Dynamics (AVD) 5.4.1 software and the value of EF in percentage was obtained. For determination of the regional function, the patients with ADA revascularization were selected. AVD analyzes the regional contractility measuring the regional longitudinal shortening (RLS) with the centerline method which consists in tracing a line in the middle of the systolic and diastolic contours which then is divided in hundred points and cords pass through them, each one reflecting the wall movement during the cardiac cycle: the longer the cord the better the movement. The longitude of each cord was corrected for the diastolic perimeter obtaining the value in percentage. The heart area in the RAO30 projection was divided in eight segments. Four of them were related with de ADA territory: basal (1), midbasal (2), midapical (3) and apical. The contractility of each area was considered as the average of the RLS of their cords. Fig. 1


   Statistical analysis of the results was executed with Excel 2000, using the difference of averages as a measure for association and the T test, type 1, for significance.

RESULTS
   Forty consecutively revascularizated patients were studied and angiographically controlled 14,39±4,77 months later. Demographic characteristics of the group are in the Table 1.


   Forty-nine arteries received a stent (1,22±0,42 arteries/patient). Fourteen presented restenosis (29%), 5 (10%) were completely occluded.

   Regarding global left ventricular function, EF before the implants was 54,87% ±13,48 (IC 95% 50,9-58,7) and after 56,52% ±16,11 (IC 95% 51,8-61,1), existing a difference of 1,65% trending toward improvement posterior the stenting, p=0,25.

   Twenty-four ADA were stented. Twenty-one of these patients were male (87,5%), 13 (54%) had a recent infarct. At the control, 12,86±3 months later, 3 (13%) had total occlusions and 10 (42%) restenosis. The regional contractility analysis in these ADA patients is shown in Table 2.

DISCUSION
   These results show an small increment in the EF of patients revascularizated with stents, difference that did not reach statistical significance. Analysis of the regional contractility after ADA stenting showed significant improvement in all the related regions but one, the midbasal. These results are consistent with those from Van Belle et al. who demonstrated a significant improvement in EF, systolic and diastolic volume indexes and in regional contractility of patients with angina or exercise-induced ischaemia, submitted to stenting. Similarly, Sirnes et al. found a 5% increase in EF and 16% in radial regional shortening of patients with occluded arteries that received stents and were opened in the four-month follow-up. Previously, experiences with balloon angioplasty in reopening suboccluded and totally occluded vessels, showed recovery of left ventricular function, global and regional, provided the flow was preserved over the time.

   Preservation of ventricular function is recognized as an important predictor of better survival. In the pre-thrombolytic era, EF and systolic volume index were considered valuable mortality markers and thereafter, in the GUSTO I angiographic substudy, parietal movement was better the earlier a TIMI 3 flow was reached and in turn, this was translated in minor mortality, fact that reinforced the open artery theory. This theory supports that fast and early coronary reperfusion is translated in better clinical outcome and survival. Reopening chronically occluded arteries is an issue still controversial. The responsible mechanisms for benefits of flow restoration beyond the time to save myocardial tissue include: better healing of infarcted areas, prevention of infarct expansion, prevention of ventricular remodeling, perfusion of stunned and hibernating myocardium and electric stabilization. It is also possible that presence of a patent artery provides collaterals to other ischaemic zones if a subsequent infarct occurs.

   There are some limitations in this study. Although an autocontrolled trial avoids the possibility for differences between comparing groups, clinical events occurring along the time were not evaluated and they could influence in any way the ventricular function. The method used to measure function parameters included the manual tracing of systolic and diastolic contours introducing certain degree of imprecision that was diminished using a single experienced and blinded observer trying to avoid interobserver differences. For the study projection we assumed a 5% alpha error and a 80% power for an expected increase of 7% in EF and 2,8% in RLS. The final results were too far from the expected ones and because of that they could not reach enough power in spite of duplicating the sample. The poor increase in parameters of global and regional contractility could be explained by the high percentage of restenosis observed in the total group and in the subgroup with ADA stenting. Perhaps, a study with selection of patients with patent artery may allow to observe the benefit clearly.

CONCLUSION
   The present trial suggests an association between late coronary stenting and improvement in global and regional left ventricular function. This functional recovery could be due to restoration of flow to stunned and hibernating myocardium, diminishing left ventricular remodeling and dilatation. This fact supports the strategy of reopening chronically occluded arteries. On the other hand, this results and others are consequent with the open artery theory and may have implications on survival of patients over the time.

 

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2nd Virtual Congress of Cardiology

Dr. Florencio Garófalo
Steering Committee
President
Dr. Raúl Bretal
Scientific Committee
President
Dr. Armando Pacher
Technical Committee - CETIFAC
President
fgaro@fac.org.ar
fgaro@satlink.com
rbretal@fac.org.ar
rbretal@netverk.com.ar
apacher@fac.org.ar
apacher@satlink.com

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