Sweden: coronary and structural heart interventions from 2010 to 2015

Sparsely populated and with wide non-urbanised areas, Sweden faces specific challenges in providing publicly financed, high-quality and equal healthcare to all parts of the country. As a result, a decentralised organisation for acute coronary care has been developed with coronary care units and catheterisation laboratories in several small- and medium-sized city areas. In contrast, highly specialised non-emergent interventional procedures are centralised to a few high-volume centres, mainly located at university hospitals in large city areas. Nationwide quality registries with nearly complete coverage facilitate healthcare quality improvement and form a basis for clinical research. In this report, we present an overview of demographics, healthcare organisation, quality registries and procedural data for coronary and structural heart interventions in Sweden over the past six years.

Intravascular Ultrasound Guidance Is Associated With Better Outcome in Patients Undergoing Unprotected Left Main Coronary Artery Stenting Compared With Angiography Guidance Alone

Background—

Small observational studies have indicated better outcome with intravascular ultrasound (IVUS) guidance when performing unprotected left main coronary artery (LMCA) percutaneous coronary intervention (PCI), but the overall picture remains inconclusive and warrants further investigation. We studied the impact of IVUS guidance on outcome in patients undergoing unprotected LMCA PCI in a Swedish nationwide observational study.

Methods and Results—

Patients who underwent unprotected LMCA PCI between 2005 and 2014 because of stable coronary artery disease or acute coronary syndrome were included from the nationwide SCAAR (Swedish Coronary Angiography and Angioplasty Registry). Of 2468 patients, IVUS guidance was used in 621 (25.2%). The IVUS group was younger (median age, 70 versus 75 years) and had fewer comorbidities but more complex lesions. IVUS was associated with larger stent diameters (median, 4 mm versus 3.5 mm). After adjusting for potential confounders, IVUS was associated with significantly lower occurrence of the primary composite end point of all-cause mortality, restenosis, or definite stent thrombosis (hazard ratio, 0.65; 95% confidence interval, 0.50–0.84) and all-cause mortality alone (hazard ratio, 0.62; 95% confidence interval, 0.47–0.82). In 340 propensity score–matched pairs, IVUS was also associated with significantly lower occurrence of the primary end point (hazard ratio, 0.54; 95% confidence interval, 0.37–0.80).

Conclusions—

IVUS was associated with an independent and significant outcome benefit when performing unprotected LMCA PCI. Potential mediators of this benefit include larger and more appropriately sized stents, perhaps translating into lower risk of subsequent stent thrombosis. Although residual confounding cannot be ruled out, our findings indicate a possible hazard when performing unprotected LMCA PCI without IVUS guidance.

Experimental validation of contrast-enhanced SSFP cine CMR for quantification of myocardium at risk in acute myocardial infarction

BACKGROUND

Accurate assessment of myocardium at risk (MaR) after acute myocardial infarction (AMI) is necessary when assessing myocardial salvage. Contrast-enhanced steady-state free precession (CE-SSFP) is a recently developed cardiovascular magnetic resonance (CMR) method for assessment of MaR up to 1 week after AMI. Our aim was to validate CE-SSFP for determination of MaR in an experimental porcine model using myocardial perfusion single-photon emission computed tomography (MPS) as a reference standard and to test the stability of MaR-quantification over time after injecting gadolinium-based contrast.

METHODS

Eleven pigs were subjected to either 35 or 40 min occlusion of the left anterior descending artery followed by six hours of reperfusion. A technetium-based perfusion tracer was administered intravenously ten minutes before reperfusion. In-vivo and ex-vivo CE-SSFP CMR was performed followed by ex-vivo MPS imaging. MaR was expressed as % of left ventricular mass (LVM).

RESULTS

There was good agreement between MaR by ex-vivo CMR and MaR by MPS (bias: 1 ± 3% LVM, r 2 = 0.92, p < 0.001), between ex-vivo and in-vivo CMR (bias 0 ± 2% LVM, r 2 = 0.94, p < 0.001) and between in-vivo CMR and MPS (bias -2 ± 3% LVM, r 2 = 0.87, p < 0.001. No change in MaR was seen over the first 30 min after contrast injection (p = 0.95).

CONCLUSIONS

Contrast-enhanced SSFP cine CMR can be used to measure MaR, both in vivo and ex vivo, in a porcine model with good accuracy and precision over the first 30 min after contrast injection. This offers the option to use the less complex ex-vivo imaging when determining myocardial salvage in experimental studies.

The safety of introducing a new generation TAVR device: one departments experience from introducing a second generation repositionable TAVR

Background

In the evolving field of transcatheter aortic valve replacements a new generation of valves have been introduced to clinical practice. With the complexity of the TAVR procedure and the unique aspects of each TAVR device, there is a perceived risk that changing or adding a new valve in a department could lead to a worse outcome for patients, especially during the learning phase. The objective was to study the safety aspect of introducing a second generation repositionable transcatheter valve (Boston Scientific Lotus valve besides Edwards Sapien valve) in a department.

Methods

In a retrospective study, 53 patients receiving the Lotus system, and 47 patients receiving the Sapien system over a period of three years were compared for short-term outcome according to VARC-2 definitions and 1-year survival.

Results

Outcome in terms VARC-2 criteria for early safety and clinical efficacy, stroke rate, and survival at 30 days and at 1 year were similar. The Lotus valve had less paravalvular leakage, where 90% had none or trace aortic insufficiency as compared to only 48% for the Sapien system.

Conclusions

Introduction of a new generation valve can be done with early device success and safety, and without jeopardizing the outcome for patients up to one year. We found no adverse effects by changing valve type and observed improved outcome in terms of lower PVL-rates. Both existing and new centers starting a TAVR program can benefit from the use of a new generation device.

Cangrelor in combination with ticagrelor provides consistent and potent P2Y12-inhibition during and after primary percutaneous coronary intervention in real-world patients with ST-segment-elevation myocardial infarction

Patients pretreated with ticagrelor with less than 1 hour from percutaneous coronary intervention (PCI) or receiving ticagrelor in cath lab were prospectively included and received cangrelor. Cangrelor was infused for 2 hours and platelet function was assessed as P2Y12 reactivity units (PRU) with the VerifyNow P2Y12 function assay before start of infusion, 15 min after the start of infusion, and 30 min after the end of infusion. A total of n = 32 patients with an average age of 68 (±13) years with n = 22 (69%) males were included. The level of P2Y12 inhibition before cangrelor infusion was started was 249 PRU (IQR 221-271). After 15 min of cangrelor infusion the P2Y12 reactivity was markedly decreased to 71 PRU (IQR 52-104, p < 0.001). At 30 min after end of infusion PRU remained within the therapeutic range, 89 PRU (IQR 50-178; p < 0.001 for comparison with preinfusion) with only n = 4 (12.5%) patients with PRU >225. Results were consistent between patients receiving ticagrelor prehospital or in the cath lab and no statistical differences in PRU were noted between the two groups in any of the three measurements. In conclusion, cangrelor in combination with ticagrelor results in consistent and strong P2Y12 inhibition during and after infusion and cangrelor may bridge the gap until oral P2Y12 inhibitors achieve effect in real-world STEMI patients undergoing primary PCI.

Contrast-Enhanced CMR Overestimates Early Myocardial Infarct Size: Mechanistic Insights Using ECV Measurements on Day 1 and Day 7

OBJECTIVES

This study aimed to investigate whether an overestimation of infarct size on cardiac magnetic resonance (CMR) versus triphenyltetrazolium chloride (TTC) exists acutely and whether it remains after 7 days in an experimental pig model and to elucidate possible mechanisms.

BACKGROUND

Overestimation of infarct size (IS) on late gadolinium enhancement CMR early after acute myocardial infarction has been debated.

METHODS

Pigs were subjected to 40 min of left anterior descending artery occlusion and 6 h (n = 9) or 7 days (n = 9) reperfusion. IS by in vivo and ex vivo CMR was compared with TTC staining. Extracellular volume (ECV) was obtained from biopsies using technetium 99m diethylenetriamine pentaacetic acid (99mTc-DTPA) and light microscopy. TTC slices were rescanned on CMR enabling slice-by-slice comparison.

RESULTS

IS did not differ between in vivo and ex vivo CMR (p = 0.77). IS was overestimated by 27.3% with ex vivo CMR compared with TTC (p = 0.008) acutely with no significant difference at 7 days (p = 0.39). Slice-by-slice comparison showed similar results. A significant decrease in ECV was seen in biopsies of myocardium at risk (MaR) close to the infarct (sometimes referred to as the peri-infarction zone) over 7 days (48.3 ± 4.4% vs. 29.2 ± 2.4%; p = 0.0025). The ECV differed between biopsies of MaR close to the infarct and the rest of the salvaged MaR acutely (48.3 ± 4.4% vs. 32.4 ± 3.2%; p = 0.013) but not at 7 days (29.2 ± 2.4% vs 25.7 ± 1.4%; p = 0.23).

CONCLUSIONS

CMR overestimates IS compared with TTC acutely but not at 7 days. This difference may be explained by higher ECV in MaR closest to the infarct acutely that decreases during 7 days to the same level as the rest of the salvaged MaR. The increased ECV in the MaR closest to the infarct day 1 could be due to severe edema or an admixture of infarcted and salvaged myocardium (partial volume) or both. Nonetheless, this could not be reproduced at 7 days. These results have implications for timing of magnetic resonance infarct imaging early after acute myocardial infarction.

Conducting Fabrics as a Shield Against Electromagnetic Interference (EMI)

The paper reports a method to design and develop a highly flexible EMI shielding material based on newly emerging technology of in situ grafting of conducting polymers onto insulating surfaces such as fabrics.

Extent of Myocardium at Risk for Left Anterior Descending Artery, Right Coronary Artery, and Left Circumflex Artery Occlusion Depicted by Contrast-Enhanced Steady State Free Precession and T2-Weighted Short Tau Inversion Recovery Magnetic Resonance Imaging

Background—

Contrast-enhanced steady state free precession (CE-SSFP) and T2-weighted short tau inversion recovery (T2-STIR) have been clinically validated to estimate myocardium at risk (MaR) by cardiovascular magnetic resonance while using myocardial perfusion single-photon emission computed tomography as reference standard. Myocardial perfusion single-photon emission computed tomography has been used to describe the coronary perfusion territories during myocardial ischemia. Compared with myocardial perfusion single-photon emission computed tomography, cardiovascular magnetic resonance offers superior image quality and practical advantages. Therefore, the aim was to describe the main coronary perfusion territories using CE-SSFP and T2-STIR cardiovascular magnetic resonance data in patients after acute ST-segment–elevation myocardial infarction.

Methods and Results—

CE-SSFP and T2-STIR data from 2 recent multicenter trials, CHILL-MI and MITOCARE (n=215), were used to assess MaR. Angiography was used to determine culprit vessel. Of 215 patients, 39% had left anterior descending artery occlusion, 49% had right coronary artery occlusion, and 12% had left circumflex artery occlusion. Mean extent of MaR using CE-SSFP was 44±10% for left anterior descending artery, 31±7% for right coronary artery, and 30±9% for left circumflex artery. Using T2-STIR, MaR was 44±9% for left anterior descending artery, 30±8% for right coronary artery, and 30±12% for left circumflex artery. MaR was visualized in polar plots, and expected overlap was found between right coronary artery and left circumflex artery. Detailed regional data are presented for use in software algorithms as a priori information on the extent of MaR.

Conclusions—

For the first time, cardiovascular magnetic resonance has been used to show the main coronary perfusion territories using CE-SSFP and T2-STIR. The good agreement between CE-SSFP and T2-STIR from this study and myocardial perfusion single-photon emission computed tomography from previous studies indicates that these 3 methods depict MaR accurately in individual patients and at a group level.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifiers: NCT01379261 and NCT01374321.

Bivalirudin versus heparin in non-ST and ST-segment elevation myocardial infarction-a registry-based randomized clinical trial in the SWEDEHEART registry (the VALIDATE-SWEDEHEART trial)

BACKGROUND

The optimal anticoagulant for patients with acute coronary syndrome treated with percutaneous coronary intervention (PCI) has not been validated in current practice of radial approach and pretreatment with potent P2Y12 inhibitors. Several studies have indicated increased bleeding rate and, in some instances, even increased mortality by the routine use of heparin and glycoprotein IIb/IIIa inhibitors compared to bivalirudin. Direct comparison of bivalirudin versus heparin alone has yielded contradictory results depending on study designs.

METHODS/DESIGN

The VALIDATE-SWEDEHEART trial is a multicenter, prospective, randomized, registry-based, controlled, and open-label clinical trial in patients with ST-segment elevation myocardial infarction (STEMI) or non-STEMI undergoing PCI pretreated with ticagrelor, prasugrel, or cangrelor. We hypothesize that bivalirudin is superior to heparin alone in reducing death, myocardial infarction, and major bleeding events at 180 days (primary end point). The trial will enroll 3,000 patients with STEMI and 3,000 patients with non-STEMI undergoing PCI. The trial will use a hybrid registry-based randomized clinical trial design where inclusion, randomization, and baseline data collection are performed using The Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies registry. The primary composite end point (death, myocardial infarction, or major bleeding events at 180 days) will be identified through active screening after 7 and 180 days and adjudicated by a blinded central end point committee. Secondary end points and long-term outcomes will be recorded from national registries.

CONCLUSION

The VALIDATE-SWEDEHEART trial is founded on a nationwide clinical registry and uses a hybrid registry-based randomized clinical trial (RRCT) design methodology to evaluate efficacy and safety of bivalirudin as compared to heparin alone for acute coronary syndrome, in a large population receiving contemporary recommended therapies including predominantly radial invasive approach and pretreatment with potent P2Y12 inhibitors.

Multi-vendor, multicentre comparison of contrast-enhanced SSFP and T2-STIR CMR for determining myocardium at risk in ST-elevation myocardial infarction

AIMS

Myocardial salvage, determined by cardiac magnetic resonance imaging (CMR), is used as end point in cardioprotection trials. To calculate myocardial salvage, infarct size is related to myocardium at risk (MaR), which can be assessed by T2-short tau inversion recovery (T2-STIR) and contrast-enhanced steady-state free precession magnetic resonance imaging (CE-SSFP). We aimed to determine how T2-STIR and CE-SSFP perform in determining MaR when applied in multicentre, multi-vendor settings.

METHODS AND RESULTS

A total of 215 patients from 17 centres were included after percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction. CMR was performed within 1-8 days. These patients participated in the MITOCARE or CHILL-MI cardioprotection trials. Additionally, 8 patients from a previous study, imaged 1 day post-CMR, were included. Late gadolinium enhancement, T2-STIR, and CE-SSFP images were acquired on 1.5T MR scanners (Philips, Siemens, or GE). In 65% of the patients, T2-STIR was of diagnostic quality compared with 97% for CE-SSFP. In diagnostic quality images, there was no difference in MaR by T2-STIR and CE-SSFP (bias: 0.02 ± 6%, P = 0.96, r(2) = 0.71, P < 0.001), or between treatment and control arms. No change in size or quality of MaR nor ability to identify culprit artery was seen over the first week after the acute event (P = 0.44).

CONCLUSION

In diagnostic quality images, T2-STIR and CE-SSFP provide similar estimates of MaR, were constant over the first week, and were not affected by treatment. CE-SSFP had a higher degree of diagnostic quality images compared with T2 imaging for sequences from two out of three vendors. Therefore, CE-SSFP is currently more suitable for implementation in multicentre, multi-vendor clinical trials.

Sample Size in Clinical Cardioprotection Trials Using Myocardial Salvage Index, Infarct Size, or Biochemical Markers as Endpoint

Background

Cardiac magnetic resonance (CMR) can quantify myocardial infarct (MI) size and myocardium at risk (MaR), enabling assessment of myocardial salvage index (MSI). We assessed how MSI impacts the number of patients needed to reach statistical power in relation to MI size alone and levels of biochemical markers in clinical cardioprotection trials and how scan day affect sample size.

Methods and Results

Controls (n=90) from the recent CHILL‐MI and MITOCARE trials were included. MI size, MaR, and MSI were assessed from CMR. High‐sensitivity troponin T (hsTnT) and creatine kinase isoenzyme MB (CKMB) levels were assessed in CHILL‐MI patients (n=50). Utilizing distribution of these variables, 100 000 clinical trials were simulated for calculation of sample size required to reach sufficient power. For a treatment effect of 25% decrease in outcome variables, 50 patients were required in each arm using MSI compared to 93, 98, 120, 141, and 143 for MI size alone, hsTnT (area under the curve [AUC] and peak), and CKMB (AUC and peak) in order to reach a power of 90%. If average CMR scan day between treatment and control arms differed by 1 day, sample size needs to be increased by 54% (77 vs 50) to avoid scan day bias masking a treatment effect of 25%.

Conclusion

Sample size in cardioprotection trials can be reduced 46% to 65% without compromising statistical power when using MSI by CMR as an outcome variable instead of MI size alone or biochemical markers. It is essential to ensure lack of bias in scan day between treatment and control arms to avoid compromising statistical power.

Automatic segmentation of myocardium at risk from contrast enhanced SSFP CMR: validation against expert readers and SPECT

BACKGROUND

Efficacy of reperfusion therapy can be assessed as myocardial salvage index (MSI) by determining the size of myocardium at risk (MaR) and myocardial infarction (MI), (MSI = 1-MI/MaR). Cardiovascular magnetic resonance (CMR) can be used to assess MI by late gadolinium enhancement (LGE) and MaR by either T2-weighted imaging or contrast enhanced SSFP (CE-SSFP). Automatic segmentation algorithms have been developed and validated for MI by LGE as well as for MaR by T2-weighted imaging. There are, however, no algorithms available for CE-SSFP. Therefore, the aim of this study was to develop and validate automatic segmentation of MaR in CE-SSFP.

METHODS

The automatic algorithm applies surface coil intensity correction and classifies myocardial intensities by Expectation Maximization to define a MaR region based on a priori regional criteria, and infarct region from LGE. Automatic segmentation was validated against manual delineation by expert readers in 183 patients with reperfused acute MI from two multi-center randomized clinical trials (RCT) (CHILL-MI and MITOCARE) and against myocardial perfusion SPECT in an additional set (n = 16). Endocardial and epicardial borders were manually delineated at end-diastole and end-systole. Manual delineation of MaR was used as reference and inter-observer variability was assessed for both manual delineation and automatic segmentation of MaR in a subset of patients (n = 15). MaR was expressed as percent of left ventricular mass (%LVM) and analyzed by bias (mean ± standard deviation). Regional agreement was analyzed by Dice Similarity Coefficient (DSC) (mean ± standard deviation).

RESULTS

MaR assessed by manual and automatic segmentation were 36 ± 10% and 37 ± 11%LVM respectively with bias 1 ± 6%LVM and regional agreement DSC 0.85 ± 0.08 (n = 183). MaR assessed by SPECT and CE-SSFP automatic segmentation were 27 ± 10%LVM and 29 ± 7%LVM respectively with bias 2 ± 7%LVM. Inter-observer variability was 0 ± 3%LVM for manual delineation and -1 ± 2%LVM for automatic segmentation.

CONCLUSIONS

Automatic segmentation of MaR in CE-SSFP was validated against manual delineation in multi-center, multi-vendor studies with low bias and high regional agreement. Bias and variability was similar to inter-observer variability of manual delineation and inter-observer variability was decreased by automatic segmentation. Thus, the proposed automatic segmentation can be used to reduce subjectivity in quantification of MaR in RCT.

CLINICAL TRIAL REGISTRATION

NCT01379261. NCT01374321.