A novel fluid-filled pressure wire avoids hydrostatic errors in physiologic measurements

Background

Hydrostatic pressure impacts intracoronary pressure measurements, generally causing overestimation of stenosis significance in the LAD and underestimation in non-LAD vessels [1–3]. Different cut-offs have been suggested for post-PCI FFR [4], corresponding to average hydrostatic effects [1–3]. Different cut-offs and stenosis misclassification may be avoided if hydrostatic effects are eliminated.

Purpose

We aimed to compare the effect of hydrostatic pressure on resting distal-to-aortic coronary pressure ratio (Pd/Pa) and FFR, using a conventional sensor-tipped- versus a novel fluid-filled pressure wire. Since the fluid-filled wire has an outside-the-body pressure transducer instead of a sensor at the tip, the fluid (saline) compensates for the hydrostatic pressure that is inside the patient's body.

Methods

We placed the sensor of a sensor-tipped wire and the measure point of a fluid-filled wire at the same location in the coronary vessel. By performing simultaneous measurements, we aimed to assess the relationship between vertical height differences and distal pressure (Pd).

We measured the vertical height difference between the tip of the guide catheter and the measure point, by changing the vertical position of the cath lab table and assessing the total distance in mm between the two table positions.

Results

The two wires were used simultaneously in 21 arteries. The lower in the coronary tree the measurements were made (e.g., in the LCX or RCA), the higher the Pd value by the conventional wire was, compared to the novel wire; the higher the measurement was made (e.g., in the LAD), the lower the Pd value.

After we corrected for hydrostatic effect on the sensor-tipped wire using the height measurement (0.77 mmHg/cm [2]), sensor-tipped wire pressure correlated better with fluid-filled wire pressure (R=0.73 vs. R=0.89 at rest and R=0.83 vs. R=0.96 at hyperaemia).

Drift was also compared in 31 simultaneous measurements. The fluid-filled wire demonstrated less drift than the sensor-tipped wire (standard deviation 0.11 vs. 0.18). With an increasing number of cases, less drift was observed, possibly learning curve-related.

Finally, we compared measurements of pressure-derived CFR using the fluid-filled wire, versus echocardiography-CFR (n=10) and bolus thermodilution-CFR (n=11). Pressure-derived CFR with the fluid-filled wire correlated to echocardiography-CFR and thermodilution-CFR (R=0.69 and R=0.76 respectively). Sensor-tipped wire pressure-derived CFR did not correlate to thermodilution-CFR measurements (n=11; R=−0.57).

Conclusions

Hydrostatic pressure introduces a variable error in conventional intracoronary pressure measurements. Resting indices are more susceptible to the hydrostatic error than hyperaemic. There is a slight learning curve associated with use of the novel wire, but hydrostatic errors in physiologic measurements can be avoided thanks to the wire's fluid-filled design and external pressure transducer.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swedish Governmental Agency for Innovation Systems (Vinnova)

Does the quality index of adherence to the evidence-based guidelines predict mortality in patients with myocardial infarction?

Background

The SWEDEHEART quality index of hospitals' adherence to the evidence-based (EB) guidelines for myocardial infarction (MI) patients has been continuously used for several decades in Sweden. The grading protocol is based on the consensus among hospitals. The hospitals are awarded points (0, 0.5, 1) for each of the 11 indicators depending on the proportion of patients who received EB treatment and achieved treatment goals. The 11 indicators at present are reperfusion treatment in STEMI (yes/no), time to-reperfusion treatment in STEMI, time to revascularisation in NSTEMI, P2Y12 antagonists at discharge, ACE-inhibitor/ARB at discharge, the proportion of patients at follow-up, smoking cessation at one-year, participation in a physical exercise program, target LDL-cholesterol and target blood pressure at one year.

Purpose

To evaluate whether the SWEDEHEART quality index predicts mortality in patients with MI.

Methods

We used data for all MI patients reported to the SWEDEHEART registry from 72 hospitals in Sweden between 2015–2021. We calculated the difference in quality index between 2021 and 2015. The hospitals were divided into quintiles based on the difference in the score. Logistic regression with log-time offset was used to adjust for confounders (age, gender, diabetes, hypertension, hyperlipidemia, STEMI/NSTEMI, cardiac arrest before admission, occupation status, history of heart failure, prior MI, prior PCI, prior CABG, cardiogenic shock).

Results

We identified 98,635 patients with MI, 32,608 (33.1%) were women and 34,198 (34.7%) had STEMI. The average age was 70.8±12.2 years. The median follow-up time was 2.7 years (IQR 1.06–4.63). The crude all-cause mortality rate was 5.5% at 30-days and 22.3% after long-term follow-up. Most hospitals (72.1%) improved their quality index on average by 3.4% per year (P<0.001). The increase in the quality index continued during COVID-19 pandemic (2020–2021) with average increase of 8.6%, 95% CI, 0.97–1.02; P<0.001. The median change in SWEDEHEART quality index score among the quintiles were −1.5 (Q1), 0,5 (Q2), 2,5 (Q3), 3 (Q4), and 4 (Q5). We found no difference in mortality between the quintiles at 30-days (OR 0.99; 95% CI 0.97–1.02; p=1.02) and long-term (OR 1.01; 95% CI 0,99–1.02; p=0.850).

Conclusion

The SWEDEHEART quality index provides valuable descriptive information about hospitals' adherence to the guidelines. However, the index, in its current form, does not predict mortality in patients with MI.

Funding Acknowledgement

Type of funding sources: None.

Predicting risk of future acute coronary syndromes, 1-year survival and the need for coronary angiography in unstable angina: a nationwide machine learning study

Background

We developed machine learning models to predict the need for coronary angiography, recurrent acute coronary syndromes (ACS) and 1-year survival in patients with chest pain and normal high-sensitivity troponins. We also studied whether hs-troponin levels within the normal range convey predictive information on these outcomes.

Purpose

We studied whether machine learning could reliably predict survival, risk of future ACS and rule out unnecessary angiographies in patients with chest pain and normal hs-troponins. We aimed to deploy these models as open-sourced web applications, to provide clinicians with individualized predictions. We also studied whether normal hs-troponin levels may serve as predictors of these outcomes.

Methods

We used the SWEDEHEART registry to include patients admitted due to chest pain, with normal high-sensitivity troponin T or I (hs-TnI, hs-TnT), who underwent angiography and did not receive a final diagnosis of acute myocardial infarction. We studied angiographic findings on segmental level, developed machine learning models for future ACS and death (within 1-year, modelled separately) and unnecessary coronary angiography, which was defined as angiography that did not lead to any intervention. Models predicting future ACS and 1-year survival included 130 candidate predictors and models for unnecessary angiography included 110 predictors. We built approximately 50'000 models, using gradient boosting, extreme gradient boosting, random forest, artificial neural networks and logistic regression.

Results

We included 9'314 patients. The 1-year mortality rate was 0.9% (n=78), rate of future ACS was 2.7% (n=251), and rate of unnecessary angiography was 61.5% (n=5455). Up to 40% had normal angiography. There was a strong association between troponin levels (within normal range) and severity of coronary atherosclerosis; e.g 32.4% in patients with hs-TnI 26–35 ng/L had &gt;50% stenosis in segment 6, as compared with 12.6% in those with hs-TnI 0–5 ng/L. All segments displayed similar associations with troponin levels. Mortality increased at hs-TnI levels above 10 ng/L for men, but not women. Age and sex adjusted hazard ratios for hs-TnI 25–35 vs hs-TnI 0–5 was 5.73 (2.14–15.35) for 1-year mortality. The strongest predictors of 1-year mortality were C-reactive protein, body mass index, estimated glomerular filtration rate, age, time from symptom onset to CCU admission, systolic blood pressure and hs-TnI. Extreme gradient boosting was the best performing model for all prediction tasks; AUC ROC in the test data sets were 0.77 for 1-year mortality, 0.77 for future ACS and 0.78 for unnecessary angiography, with excellent calibration.

Conclusion

Machine learning models can reliably predict 1-year risk of death or ACS, as well as predict unnecessary angiographies. Troponin levels within normal range constitute a strong predictor of all these outcomes, questioning the definition of normal troponin.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Sahlgrenska University hospital

Comparative Effectiveness of CABG versus PCI in Patients with Ischemic Heart Disease: insights from SWEDEHEART Registry

Background

Several studies have compared CABG to PCI as revascularization treatment in patients with ischemic heart disease (IHD). However, it remains unclear which revascularization strategy carries survival benefits in the long-term.

Methods

We used data from the SWEDEHEART (Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) registry for all hospital admissions at 13 cardiac care centers within Västra Götaland County in Sweden (∼20% of all SWEDEHEART data). The database contains &gt;1000 clinical variables documenting the entire process of acute coronary hospital care. All patients hospitalized for stable angina or NSTE-ACS during the period 2000–2018 were included in the analysis. We used a propensity score-adjusted Cox proportional-hazards regression with hospitals as random-effect variables. We adjusted for patients' demographics, socio-economic status, traditional risk factors, comorbidities, the severity of coronary artery disease, left ventricular function, calendar year and medication at discharge. For sensitivity analysis, we used the instrumental variable estimator for the Cox proportional-hazards model (with treating hospital as a treatment-preference instrument) to simultaneously deal with the problems of unmeasured confounding and censoring of the outcome. The primary outcome was all-cause mortality.

Results

In total, 11,896 patients were included in the study. Of these, 3,129 (26.3%) were women. 20.4% had diabetes and 10.4% had a previous myocardial infarction. The mean age was 66.7±10.7, and 42.9% were &gt;70 years old. 61.5% had three-vessel and/or left main disease. Median follow-up time was 5.7 years (range 1 day-18.2 years). Revascularization therapy after coronary angiography was PCI in 9449 (79.4%) and CABG in 2,447 (20.6%) patients. CABG patients were more likely to have diabetes, left main/multivessel disease and heart failure. The number of revascularized patients with PCI increased by 6.4% per calendar year (P&lt;0.001). There were 2,481 (20.9%) deaths. CABG was associated with a lower risk of death compared to PCI (HR 0.81; 95% CI 0.69–0.95; P=0.011. We found no evidence for treatment heterogeneity between the revascularization strategy and age, gender, diabetes, heart failure and indication for revascularization (all P-interaction &gt;0.05). Results from the sensitivity analysis support the conclusions from the primary model.

Conclusions

In hospitalized patients due to IHD, revascularization with CABG was associated with superior long-term survival compared to PCI.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Heart and Lung Foundation, ALF Västra Götaland, Swedish Scientific Council

Long-term survival in patients with coronary artery disease undergoing percutaneous coronary intervention with or without intracoronary pressure wire guidance: a report from SCAAR

Background

Intracoronary pressure wire measurements of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) provide decision-making guidance during percutaneous coronary intervention (PCI). However, limited data exist on the impact of FFR/iFR on long-term clinical outcomes in patients with stable angina, unstable angina (UA)/non-ST-segment elevation myocardial infarction (NSTEMI), or STEMI.

Methods

We used data from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR) on all patients in Sweden undergoing PCI (with or without FFR/iFR guidance) for stable angina, UA/NSTEMI, or STEMI between January 2005 and March 2018. The primary endpoint was all-cause mortality and the secondary endpoints were stent thrombosis or restenosis and periprocedural complications. The primary model was multilevel Cox proportional-hazards regression using an instrumental variable (IV) to adjust for known and unknown confounders with treating hospital as a treatment-preference instrument. The following variables were entered into Cox proportional-hazards regression in addition to the IV: age, sex, diabetes, indication for PCI, severity of coronary disease, smoking status, hypertension, hyperlipidemia, previous myocardial infarction, previous PCI, previous coronary artery bypass graft, type of stent.

Results

In total, 151,001 patients underwent PCI: 31,514 (20.9%) for stable angina, 74,982 (49.6%) for UA/NSTEMI, and 44,505 (29.5%) for STEMI. Of these, FFR/iFR guidance was used in 11,433 patients (7.6%): 5029 (44.0%) with stable angina, 5989 (52.4%) with UA/NSTEMI, and 415 (3.6%) with STEMI; iFR was used in 1156 (10.1%) of these patients. After a median follow-up of 1784 (range 1–4824) days, the FFR/iFR group had lower adjusted risk estimates for all-cause mortality [hazard ratio (HR) 0.79; 95% confidence interval (CI) 0.69–0.91; P=0.001] and stent thrombosis and restenosis (HR 0.13; 95% CI 0.09–0.19; P&lt;0.001). The number of periprocedural complications did not differ significantly between the groups (odds ratio 0.69; 95% CI 0.30–1.55; P=0.368). There was no interaction between FFR/iFR and indication for PCI. We found no difference between FFR and iFR (HR 1.12; 95% CI 0.90–1.59; P=0.216).

Conclusions

In this observational study, the use of FFR/IFR was associated with a lower risk of long-term mortality in patients undergoing PCI for stable angina, UA/NSTEMI, or STEMI. Our study supports the current European and American guidelines for the use of FFR/iFR during PCI and shows that intracoronary pressure wire guidance has prognostic benefit in patients with stable angina as well as in patients with the acute coronary syndrome.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Heart and Lung Foundation, ALF Västra Götaland, Swedish Scientific Council

Importance of circulating IGF-1 for normal cardiac morphology, function and post infarction remodeling

IGF-1 plays an important role in cardiovascular homeostasis, and plasma levels of IGF-1 correlate inversely with systolic function in heart failure. It is not known to what extent circulating IGF-1 secreted by the liver and local autocrine/paracrine IGF-1 expressed in the myocardium contribute to these beneficial effects on cardiac function and morphology. In the present study, we used a mouse model of liver-specific inducible deletion of the IGF-1 gene (LI-IGF-1 -/- mouse) in an attempt to evaluate the importance of circulating IGF-I on cardiac morphology and function under normal and pathological conditions, with an emphasis on its regulatory role in myocardial phosphocreatine metabolism. Echocardiography was performed in LI-IGF-1 -/- and control mice at rest and during dobutamine stress, both at baseline and post myocardial infarction (MI). High-energy phosphate metabolites were compared between LI-IGF-1 -/- and control mice at 4 weeks post MI. We found that LI-IGF-1 -/- mice had significantly greater left ventricular dimensions at baseline and showed a greater relative increase in cardiac dimensions, as well as deterioration of cardiac function, post MI. Myocardial creatine content was 17.9% lower in LI-IGF-1 -/- mice, whereas there was no detectable difference in high-energy nucleotides. These findings indicate an important role of circulating IGF-1 in preserving cardiac structure and function both in physiological settings and post MI.