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The meta-analysis and regression of 7714 ULMCAD patients to compare productivity of bypass surgery and drug-eluting stents as treatment procedures

 Background

The efficiency of a drug-eluting stent (DES) in individuals suffering from the ULMCAD disease (unprotected left main coronary artery disease) for a long period of time in contrast to coronary artery bypass surgery (CABG) continues to baffle clinicians in any trials conducted. When data from these trials is observed over a long time, it is sometimes inadequate to draw conclusions on. By employing the use of prevalent survey methods, we wish to analyze the clinical effects of both DES and CABG procedures over a long time through the meta-analysis procedure of big data pooled from randomized controlled experiments.

Methods

Articles published in scholarly journals such as PubMed, Cochrane Library, EMBASE, Google Scholar, Medline related to compare incidences of PCI (percutaneous coronary intervention) using CABG in ULMCAD with at least 5-year follow-up were identified. Data from these journals and relevant references was then statistically analyzed.

Results

 For the initial stage, 10 cases were identified. The identified cases consisted of 7714 patients, of whom 3803 were under PCI and 3911 under the CABG procedure. A significant variability was observed in the long term in the follow-up to repeat revascularization (OR 2.78, 95% CI 2.11–3.68, P < .00001) and myocardial infarction of (OR 1.57, 95% CI 1.16–2.11, P = .0003). The bypass surgery procedure (CABG) was observed to be superior and have a lower number of associated risks in comparison to PCI. The mortality rate and major adverse cardiovascular and cerebrovascular events (MACCE) was observed have a similarity over the two categories (OR 0.91 95% CI 0.73-1.13, P=0.37) and (OR 1.22 95% CI 0.95-1.56, P= 0.12) respectively. The PCI set was also identified to have a statistically significant lower chance of stroke (OR 0.5 95% CI 0.28-0.91, P= 0.02). It was also determined that a low SYNTX score in the PCI category relatively implied a low risk of revascularization within the same group (regression coefficient =0.109, P = .010). Patients low on the SYNTAX score are more suited to PCI for ULMCAD. The risk of revascularization and MI however, continue to be critical clinical concerns.

Introduction

A proportion of 4-6% of individuals undertaking coronary angiography1 suffer from the left main coronary artery disease. Several events have been identified, but the higher number of common acute cardiovascular events experienced in ULMCAD patients are increased morbidity and high mortality rates. The higher efficiency observed in bypass surgery procedures and better survival chances of CABG facilitated its recommendation as a standard ULMCAD treatment procedure in comparison to medical therapy2,3. The PCI method employs the use of bare metal stents and was put into place in order to assist in the treatment of high surgical risk patients4. Rates of mortality and major cardiovascular complications for the PCI method however, remained higher than those observed in CABG, leading to the affirmation of CABG by the American College of Cardiology/American Heart Association (ACC/AHA) to be used as a treatment procedure in the management of left main coronary artery disease. In the recent past, interventional cardiology experienced a significant change during DES medication in patients classified to have a high surgery risk, but inconsistency in its results reduced its application in modern medicine and further confirmed the superiority of CABG.  Several meta-analysis surveys5,6 using randomized trials have been carried out, but with variant results. In response to this, we carried out this large, up-to-date meta-analysis randomized survey using modern data and longer follow-up periods in order to assess the efficiency of both PCI and CABG as treatment options of ULMCAD.

 

Methods

Figure 1 illustrates the meta-analysis flow chart used in this study. As in Table 1, we used PubMed, Google Scholar, EMBASE, Medline and relevant articles as the sources of data to be analyzed. All the information in these sources was already published, and we therefore required no patient consent or ethical approval. 2 investigators were used to identify and scrutinize all the relevant material from the aforementioned 5 databases to ensure only the highly qualified survey reports were used. The main keywords used in the search included “drug-eluding stents”, “bypass surgery”, “left main stenting”, “CABG versus PCI” and “left main disease”. Once scrutinized, data and clinical results of the identified studies were extracted independently. This independent extraction was carried out in order to reduce instances of missing observations, missing data and errors. The score card for a study to be identified was if it had (i) a clinical follow-up of more than 5 years (ii)a comparison between CABG and PCI (focusing on DESs only) and (iii) random or nonrandomized clinical trials. Any researches that (i) failed to compare CABG with PCI (ii) included individuals suffering from acute coronary syndrome (iii) had unclear content (iv) aimed at individuals suffering from chronic conditions and (v) contrasted CABG against bare metal stents were ruled out from this analysis. The Cochrane Collaboration formula was used to assess the risk of bias for studies that had been included for analysis7, and the Jadad score (0-5)8 used to ascertain the merit of randomized studies. The score of observational studies on quality was gauged through the Newcastle-Ottawa Scale (NOS)9, and needed a score of at least 7 in order to be reviewed to be of high quality. Review Manager of Version 5.3 was applied to analyze pooled data. The RevMan software is available on http://tech.cochrane.org/revman. The results which formed the comparison basis for these studies were myocardial infarction (MI), MACCE, stroke, all-cause mortality and incidences of repeat revascularization after 5 follow-up years. We applied the Mantel- Haenszel statistical procedure with randomization. The odds ratios (ORs) and confidence intervals were applied to estimate the effect sizes of each clinical outcome. In our study, MACCE was reviewed to encompass revascularization. The Dixon’s Q test with the I2 test was applied to investigate heterogeneity among the studies. In this study, we evaluated a P value of <.1 and a score of >50% to be statistically significant. A leave-one-out approach was also used, when necessary, in order to account for any heterogeneity so realized.

 

Results

Our research consisted of 3803 patients in PCI and 3911 in CABG  from a total of 7714 individuals. 7 observational evaluations of PCI/DES against CABG for ULMCAD and 3 randomized controlled experiments were identified (Table 1). All of the 10 earmarked studies had a minimum of 5 years in follow-up. The random controlled experiments we used were SYNTAX, PRE-COMBAT and NOBLE trials. These were Synergy of the Percutaneous Coronary Intervention with TAXUS and Cardiac Surgery, Bypass Surgery against Angioplasty through the use of Sirolimus-Eluting Stent in individuals suffering from Left Main Coronary Artery Disease and Percutaneous Coronary Angioplasty versus Coronary Artery Bypass Grafting in Treatment of Unprotected Left Main Stenosis respectively. Table 1 shows the time period for follow-up and their baseline characteristics as observed whereas Figures (2, 3) show the risk of bias associated with the studies contained in this study. Although the observational evaluations had an expectation of bias, they were observed to have quality clinical models and data outcomes, as shown in Table 3.

It was observed that based on revascularization, PCI was inferior to CABG. CABG was observed to have a MI of (OR 1.57, 95% CI 1.16–2.11, P = .0003) and (OR 2.78, 95% CI 2.11–3.68, P < .00001) on revascularization. No significant disparity was observed in the rate of mortality (OR 0.91 95% CI 0.73-1.13, P=0.37) or in MACCE (OR 1.22, 95% CI 0.95–1.56, P = .12) for the two categories of ULMCAD treatment. However, the PCI category had a lower risk of stroke, observed to be OR 0.5, 95% CI 0.28–0.91, P = .002 (Figure 2-6).

Revascularization and outcomes of stroke were observed to be significantly heterogeneous in the two categories. When analyzed through the leave-one-out approach, the high heterogeneity in stroke was attributed to the NOBLE trial. The outcomes of revascularization were observed to not hold a parallel impact and as a result, meta-regression analysis was carried out.

For meta-regression, 5 baseline attributes were applied. They included (i) diabetes mellitus (ii) hypertension (iii) number of male subjects (iv) SYNTAX score and (v) ejection fraction of the heart’s left ventricle. As shown in the supplementary file, SYNTAX was the sole covariant that had an effect of size in the two groups and had a regression coefficient of 0.109 (P=.010). SYNTAX score is directly proportional to the risk of revascularization.

Discussion

Patient and operative safety in PCI for ULMCAD continues to be a critical concern among interventional cardiologists. Several researches and randomized trials have been carried out but have continuously yielded inconsistent results. Disparate follow-up periods have also been meta-analyzed10, 11 and yielded different results, bringing into light the possibility of time-sensitive variable outcomes. Through this study, we therefore wish to evaluate the safety and feasibility of PCI/DES for ULMCAD patients.

The analysis we conducted demonstrated that a substantial number of individuals had a repeat revascularization procedure after a 5-year period of follow-up (OR 2.78, 95% CI 2.11–3.68, P < .00001) as illustrated by Figure 4. We also incorporated target vessel and de-novo lesions in repeat revascularization for a more conclusive meta-analysis. The revascularization of left main coronary artery disease target was equivalent within the two categories in NOBLE trials (PCI 21% vs. CABG 8%, P= 0.37) as shown in Table 1. In a CABD procedure, narrowed and blocked coronary arteries are eluded and an alternative channel is created. This property shields the patient from further episodes of ischemia in the bypassed segment. The stent grafts introduced to the distal left main disease and bifurcation procedures have been realized to substantially increase operative risks and the chances of repeat revascularization.12

A randomized experiment of DKCRUSH-V (Double Kissing and Double Crush Versus Provisional T Stenting Technique for the Treatment of Unprotected Distal Left Main True Bifurcation Lesions) 3 was recently published. The research deduced that a lower ratio of failure of target lesion within an year can be achieved through usage of a double kissing crush 2-stent approach as opposed to the existing stent approach. However, subsequent studies conducted earlier on the efficiency of the provisional stenting on the proximal segment had better results. A consequential heterogeneity between trials was observed in our research thus prompting the need for meta-regression (supplemental file). The only covariant that demonstrated effect of size was the SYNTAX score, which showed to be relatively directly proportional to the risk of revascularization. The results we realized were in congruence to those of the SYNTAX trial as shown in Table 1. A SYNTAX score ≥ 33 increased chances of repeat revascularization in patients but the chances had no change in the 2 groups whose score was 0-32: (P <.001 vs P= .36) respectively. Repeat revascularization in EXCEL however, displayed different results on the relativity of a SYNTAX score to the likelihood of repeat revascularization for a follow-up of 3 years. This experimental inconsistency may lay doubt on the functioning of SYNTAX score in determining the treatment method in patients suffering from ULMCAD.

As displayed in Figure 5, we further observed that patients under the PCI category had more follow-up incidences of myocardial infarction and hence the high rate of revascularization. Superiority of the CABG procedure exhibited itself in the NOBLE trial, where a (HR 2.88, 95% CI 1.40–5.90, P = .004) (Table 1) was observed. The de-novo lesions also required higher amounts of revascularization. However, the MI results for the two categories was the same for the PRECOMBAT and SYNTAX trials (Table 1). It is critical to observe that when implemented within the SYNTAX trial, the corresponding SYNTAX score registered no substantial effect on MI. The clinical definition of MI was not definite throughout the studies analyzed thereby causing limitations in its interpretation.

An increase in MI and revascularization rates within the PCI group did not lead to a corresponding change in mortality or the effect of MACCE (OR 0.83 95% CI 0.60-1.15, P=0.26) and (OR 1.22 95% CI 0.95-1.56, P= 0.12) respectively (Figure 6, 7). The outcomes realized in our study were similar to those achieved under the PRECOMBAT trials (mortality P=.32, MACCE P= .26) (Table 1). The MACCE outcome after a 5-year follow-up in the NOBLE trials was however promising for patients in CABG (HR 1.48, CI 95%   1.11-1.96, P=.0066) (Table 1). The same propitious MACCE advantage exhibited itself in SYNTAX score patients who had a higher SYNTAX score and under the CABG category (HR 1.78, CI 95% 1.21-2.63, P=.003) (Table 1).  No substantial difference was observed in mortality rates of the two categories for the randomized and un-randomized trials. However, one study (exempted from our analysis) reported an increase in mortality for the PCI category at a period of 5 years16. This specific study had outcomes that were a challenge to draw out, hence its exemption.

The selected studies had a heterogeneity of about 60% on the incidences of stroke in the PCI group (Figure 8). Stroke, however, was significantly low in the same category and to investigate the effect of the realized heterogeneity, a leave-one-out analysis protocol was put in place. Subjects of the NOBLE trial under PCI were observed to have a high chance of experiencing stroke, and the cause for this was undefined (Figure 9). It was however noted that the stroke mainly manifested itself once the patient stopped receiving dual antiplatelet therapy (after an year). Discontinuation of the treatment procedure may result in a rebound of the prothrombotic conditions, especially if the discontinuation is not gradual. A rebound of these effects may in turn intensify the risk of ischemic stroke13. In a study conducted by Athappan et al14, patients under the PCI group were identified to have a lower incidence of stroke compared to those under the CABG procedure when observed on a span of 5 years.

In another study, Kosmidou et al15 used meta-analysis to investigate the differences in the application of atrial fibrillation in both the CABG and PCI approaches under the EXCEL experiment. The study observed that incidence of the new onset of atrial fibrillation was more pronounced within CABG patients in comparison to those belonging to the PCI category (18.0% CABG versus 0.1% PCI, P<0001). In as much as the CABG methodology is superior to the PCI procedure, several other facets require to be examined in order to assess their significance in creating precautionary measures for increased efficiency of the CABG procedure.

Limitations

The research we conducted is subject to several shortcomings. The inclusion and exclusion approach we applied may have resulted in bias, and such an event was purely unintentional. We may have probed deeper in an attempt to account for the significant heterogeneity realized and in doing so, disregarded some latent clinical variables. These latent variables also have an effect on the realized results but they are not catered for. Also, in the several studies we analyzed, MI was defined differently in each of them. Our interpretation could therefore be slightly different from its clinical definition. The preference of the observation studies to be analyzed also had a high risk of bias. Lastly, studies containing more opposing results may not have been published in the databases at the time of the research.

Conclusion

PCI/DES in ULMCAD was observed to have a higher number of MI and revascularization during follow-ups over a long period of time as opposed to CABG. A low risk of revascularization was attributed to a low-ranking SYNTAX score when analyzed using meta-regression.