A comparison of different methods to maximise signal extraction when using central venous pressure to optimise atrioventricular delay after cardiac surgery

Objective

Our group has shown that central venous pressure (CVP) can optimise atrioventricular (AV) delay in temporary pacing (TP) after cardiac surgery. However, the signal-to-noise ratio (SNR) is influenced both by the methods used to mitigate the pressure effects of respiration and the number of heartbeats analysed. This paper systematically studies the effect of different analysis methods on SNR to maximise the accuracy of this technique.

Methods

We optimised AV delay in 16 patients with TP after cardiac surgery. Transitioning rapidly and repeatedly from a reference AV delay to different tested AV delays, we measured pressure differences before and after each transition. We analysed the resultant signals in different ways with the aim of maximising the SNR: (1) adjusting averaging window location (around versus after transition), (2) modifying window length (heartbeats analysed), and (3) applying different signal filtering methods to correct respiratory artefact.

Results

(1) The SNR was 27 % higher for averaging windows around the transition versus post-transition windows. (2) The optimal window length for CVP analysis was two respiratory cycle lengths versus one respiratory cycle length for optimising SNR for arterial blood pressure (ABP) signals. (3) Filtering with discrete wavelet transform improved SNR by 62 % for CVP measurements. When applying the optimal window length and filtering techniques, the correlation between ABP and CVP peak optima exceeded that of a single cycle length (R = 0.71 vs. R = 0.50, p < 0.001).

Conclusion

We demonstrated that utilising a specific set of techniques maximises the signal-to-noise ratio and hence the utility of this technique.

Complete revascularization is associated with higher mortality in patients with ST-elevation myocardial infarction, multi-vessel disease and shock defined by hyperlactataemia: results from the Harefield Shock Registry incorporating explainable machine learning

AIMS

Revascularization strategy for patients with ST-elevation myocardial infarction (STEMI) and multi-vessel disease varies according to the patient's cardiogenic shock status, but assessing shock acutely can be difficult. This article examines the link between cardiogenic shock defined solely by a lactate of ≥2 mmol/L and mortality from complete vs. culprit-only revascularization in this cohort.

METHODS AND RESULTS

Patients presenting with STEMI, multi-vessel disease without severe left main stem stenosis and a lactate ≥2 mmol/L between 2011 and 2021 were included. The primary endpoint was mortality at 30 days by revascularization strategy for shocked patients. Secondary endpoints were mortality at 1 year and over a median follow-up of 30 months. Four hundred and eight patients presented in shock. Mortality in the shock cohort was 27.5% at 30 days. Complete revascularization (CR) was associated with higher mortality at 30 days [odds ratio (OR) 2.1 (1.02-4.2), P = 0.043], 1 year [OR 2.4 (1.2-4.9), P = 0.01], and over 30 months follow-up [hazard ratio (HR) 2.2 (1.4-3.4), P < 0.001] compared with culprit lesion-only percutaneous coronary intervention (CLOP). Mortality was again higher in the CR group after propensity matching (P = 0.018) and inverse probability treatment weighting [HR 2.0 (1.3-3.0), P = 0.001]. Furthermore, explainable machine learning demonstrated that CR was behind only blood gas parameters and creatinine levels in importance for predicting 30-day mortality.

CONCLUSION

In patients presenting with STEMI and multi-vessel disease in shock defined solely by a lactate of ≥2 mmol/L, CR is associated with higher mortality than CLOP.

How robust are recommended waiting times to pacing after cardiac surgery that are derived from observational data?

AIMS

For bradycardic patients after cardiac surgery, it is unknown how long to wait before implanting a permanent pacemaker (PPM). Current recommendations vary and are based on observational studies. This study aims to examine why this variation may exist.

METHODS AND RESULTS

We conducted first a study of patients in our institution and second a systematic review of studies examining conduction disturbance and pacing after cardiac surgery. Of 5849 operations over a 6-year period, 103 (1.8%) patients required PPM implantation. Only pacing dependence at implant and time from surgery to implant were associated with 30-day pacing dependence. The only predictor of regression of pacing dependence was time from surgery to implant. We then applied the conventional procedure of receiver operating characteristic (ROC) analysis, seeking an optimal time point for decision-making. This suggested the optimal waiting time was 12.5 days for predicting pacing dependence at 30 days for all patients (area under the ROC curve (AUC) 0.620, P = 0.031) and for predicting regression of pacing dependence in patients who were pacing-dependent at implant (AUC 0.769, P < 0.001). However, our systematic review showed that recommended optimal decision-making time points were strongly correlated with the average implant time point of those individual studies (R = 0.96, P < 0.001). We further conducted modelling which revealed that in any such study, the ROC method is strongly biased to indicate a value near to the median time to implant as optimal.

CONCLUSION

When commonly used automated statistical methods are applied to observational data with the aim of defining the optimal time to pacing after cardiac surgery, the suggested answer is likely to be similar to the average time to pacing in that cohort.

The BE-ALIVE score: assessing 30-day mortality risk in patients presenting with acute coronary syndromes

AIM

To create and validate a simple scoring system for predicting 30-day mortality in patients presenting with acute coronary syndromes (ACS) at their moment of admission.

METHODS AND RESULTS

2407 consecutive patients presenting to Harefield Hospital with measured arterial blood gases, from January 2011 to December 2020, were studied to build the training set. 30-day mortality in this group was 17.2%. A scoring algorithm that was built using binary logistic regression of variables available on admission was then converted to an additive risk score. The resultant scoring system is the BE-ALIVE score, which incorporates the following factors:Base Excess (1 point for <-2 mmol/L), Age (<65 years: 0 points, 65-74: 1 point, 75-84: 2 points, ≥85: 3 points), Lactate (<2 mmol/L: 0 points, 2-4.9: 1 point, 5-9.9: 3 points, ≥10: 6 points), Intubated (2 points), Left Ventricular function (mildly impaired or better: -1 point, moderately impaired: 1 point, severely impaired: 3 points) and External/out of hospital cardiac arrest 2 points).The scoring system was validated using a testing set of 515 patients presenting to Harefield Hospital in 2021. The validation metrics were excellent with a c-statistic of 0.9, Brier's score 0.06 vs a naïve classifier of 0.15, Spiegelhalter's z-statistic probability of 0.267 and a calibration slope of 1.08.

CONCLUSION

The BE-ALIVE score is a simple and accurate scoring system to predict 30-day mortality in patients presenting with ACS. Appreciating this mortality risk can allow prompt involvement of appropriate care such as the shock team.

Right ventricular failure: Current strategies and future development

Right heart failure can be defined as a clinical syndrome consisting of signs and symptoms of heart failure resulting from right ventricular dysfunction. Function is normally altered due to three mechanisms: (1) pressure overload (2) volume overload, or (3) a decrease in contractility due to ischaemia, cardiomyopathy or arrythmias. Diagnosis is based upon a combination of clinical assessment plus echocardiographic, laboratory and haemodynamic parameters, and clinical risk assessment. Treatment includes medical management, mechanical assist devices and transplantation if recovery is not observed. Distinct attention to special circumstances such as left ventricular assist device implantation should be sought. The future is moving towards new therapies, both pharmacological and device centered. Immediate diagnosis and management of RV failure, including mechanical circulatory support where needed, alongside a protocolized approach to weaning is important in successfully managing right ventricular failure.

Long-term outcomes following catheter ablation versus medical therapy in patients with persistent atrial fibrillation and heart failure with reduced ejection fraction

AIMS

The ARC-HF and CAMTAF trials randomized patients with persistent atrial fibrillation (AF) and heart failure (HF) to early routine catheter ablation (ER-CA) versus pharmacological rate control (RC). After trial completion, delayed selective catheter ablation (DS-CA) was performed where clinically indicated in the RC group. We hypothesized that ER-CA would result in a lower risk of cardiovascular hospitalization and death versus DS-CA in this population.

METHODS AND RESULTS

Overall, 102 patients were randomized (age 60 ± 11 years, left ventricular ejection fraction [LVEF] 31 ± 11%): 52 to ER-CA and 50 to RC. After 12 months, patients undergoing ER-CA had improved self-reported symptom scores, lower New York Heart Association class (i.e. better functional capacity), and higher LVEF compared to patients receiving RC alone. During a median follow-up of 7.8 (interquartile range 3.9-9.9) years, 27 (54%) patients in the RC group underwent DS-CA and 34 (33.3%) patients died, including 17 (32.7%) randomized to ER-CA and 17 (34.0%) randomized to RC. Compared with DS-CA, a strategy of ER-CA exhibited similar risk of all-cause mortality (adjusted hazard ratio [aHR] 0.89, 95% confidence interval [CI] 0.44-1.77, p = 0.731) and combined all-cause mortality or cardiovascular hospitalization (aHR 0.80, 95% CI 0.43-1.47, p = 0.467). However, analyses according to treatment received suggested an association between CA and improved outcomes versus RC (all-cause mortality: aHR 0.43, 95% CI 0.20-0.91, p = 0.028; all-cause mortality/cardiovascular hospitalization: aHR 0.48, 95% CI 0.24-0.94, p = 0.031).

CONCLUSIONS

In patients with persistent AF and HF, ER-CA produces similar long-term outcomes to a DS-CA strategy. The association between CA as a treatment received and improved outcomes means there is still a lack of clarity regarding the role of early CA in selected patients. Randomized trials are needed to clarify this question.

Real-world intravascular ultrasound (IVUS) use in percutaneous intervention-naïve patients is determined predominantly by operator, patient, and lesion characteristics

BACKGROUND

Intravascular Ultrasound (IVUS) has been shown to improve clinical outcomes in patients undergoing percutaneous intervention (PCI) in numerous trials. However, it is still underutilized outside of trial settings, and most trials include a significant proportion of patients with prior PCI. The aim of this study is to look at real-world use and outcomes in PCI-naïve patients who undergo IVUS-guided intervention.

METHODS AND RESULTS

Prospectively collected data from 10,574 consecutive patients undergoing their index PCI was retrospectively analyzed. 455 (4.3%) patients underwent IVUS, with a median follow-up of 4.6 years. Patients undergoing IVUS had higher levels of comorbidities including diabetes (27.5% vs. 19.7%, p < 0.001), hypertension (58.0% vs. 47.9%, p < 0.001), hypercholesterolemia (51.6% vs. 39.2%, p < 0.001) and were generally older (65.9 ± 14.5 vs. 64.5 ± 13.4 years, p = 0.031) with higher mean baseline creatinine levels (95.4 ± 63.3 vs. 87.8 ± 46.1 μmol/L). The strongest predictor of IVUS use was the operating consultant graduating from medical school after the year 2000 [OR 14.5 (3.5-59.8), p < 0.001] and the presence of calcific lesions [OR 5.2 (3.4-8.0) p < 0.001]. There was no significant difference in MACE nor 1-year mortality between patients undergoing IVUS-guided or angiography-only PCI on unadjusted analysis [OR 1.04 (0.73-1.5), p = 0.81, OR 1.055 (0.65-1.71) p = 0.828] nor mortality throughout the study period (HR 0.93 (0.69-1.26), p = 0.638). This held true for stents longer than 28 mm. Propensity matched analysis of patients similarly showed no mortality difference between arms for all patients and those with longer stents (p = 0.564 and p = 0.919).

CONCLUSION

The strongest predictors of IVUS use in PCI-naïve patients are the operator's year of graduation from medical school and proxy measures of calcific lesions. On both matched and adjusted analysis there was no evidence of improved mortality nor reduced MACE in this specific retrospective cohort, although this may well be explained by significant selection bias.

Techniques to aid prediction of pacing dependence at 30 days in patients requiring pacemaker implantation after cardiac surgery

Permanent pacemaker (PPM) implantation occurs in up to 5 % of patients after cardiac surgery but there is little consensus on how long to wait between surgery and PPM insertion. Predicting the likelihood of a patient being pacing dependent 30 days after implant can aid with this timing decision and avoid unnecessary observation time waiting for intrinsic conduction to recover. In this paper, we introduce a new approach for the prediction of PPM dependency at 30 days after implant in patients who have undergone recent cardiac surgery. The aim is to create an automatic detection model able to support clinicians in the decision-making process. We first applied Synthetic Minority Oversampling Technique (SMOTE) and Bayesian Networks (BN) to the dataset, to balance the inherently imbalanced data and create additional synthetic data respectively. The six resultant datasets were then used to train four different classifiers to predict pacing dependence at 30 days, all using the same testing set. The Bagged Trees classifier achieved the best results, reaching an area under the receiver operating curve (AUC) of 90 % in the train phase, and 83 % in the test phase. The overall classification performance was clearly enhanced when using SMOTE and synthetic data created with BN to create a combined and balanced dataset. This technique could be of great use in answering clinical questions where the original dataset is imbalanced.

Optimal timing of pacemaker implantation after cardiac surgery: should we wait 12 days? A 5-year observational study from a UK tertiary centre

Funding Acknowledgements

Type of funding sources: None.

Background and Purpose

Post-operative bradycardia is common but intrinsic rhythm often recovers. There is little consensus on the optimum time to wait between cardiac surgery and the implantation of a permanent pacemaker (PPM). Earlier device implantation may facilitate shorter length of stay. However, it may expose some patients who have no long-term pacing requirement to the risks associated with device therapy. This study aimed to understand how the number of days between cardiac surgery and PPM implantation is associated with pacing dependence and recovery of intrinsic conduction by 30 days.

Methods

We examined healthcare records of consecutive patients who underwent cardiac surgery at our centre between 01/01/2015 to 01/01/2021. The primary outcome measures were pacing dependence (PD) at 30 days and recovery of intrinsic conduction at 30 days. Recovery was defined as showing evidence of intrinsic rhythm at the 30 day check after being pacing dependent at the time of implant. Patient demographics, baseline ECG characteristics and surgical procedure were recorded. Time to pacemaker implantation and pacing indication were identified.

Pacing checks at 30 days post implant were reviewed and PD defined as no intrinsic rhythm seen over a 30 second period with base rate set at 40bpm. Univariate analysis and binary logistic regression were used to determine factors significantly associated with the primary outcome measures. Subsequent receiver-operator characteristic (ROC) analysis was used to determine the optimal timing of pacemaker implantation as defined by the Youden Index. This aims to maximise sensitivity and specificity of days to implant in predicting PD and conduction recovery at 30 days.

Results

Following 5849 operations, 103 (1.8%) patients underwent PPM implantation for a new bradycardic indication. The baseline characteristics of those paced are summarised in table 1. Numerous factors were associated with pacing dependence at 30 days on univariate analysis (table 2). However, multivariate analysis showed that only PD at implant and days to implant (DTI) were significant predictors of PD at 30 days. The only significant association with conduction recovery was DTI.

ROC analysis showed that the optimal DTI is 12 days for a variety of analyses: 1.) Predicting PD at 30 days for all patients (AUC 0.620, SE 0.056, p=0.031, 95% CI 0.511-0.730) 2.) Predicting PD in patients whose PPM indication was AV nodal dysfunction (AUC 0.706, p=0.001, Youden Index (YI) 1.34). 3.) Predicting recovery of intrinsic rhythm in patients who were pacing dependent at implant (AUC 0.80, p= 0.000, YI 1.515).

Conclusions

The number of days between surgery and pacemaker implantation is the only factor significantly associated with both pacing dependence and recovery of intrinsic conduction at 30 days. The optimum time to wait is 12 days to allow time for intrinsic conduction to recover.

Using base excess, albumin, lactate and renal function to predict 30-day mortality in patients requiring impella monotherapy for left-sided mechanical circulatory support: The BALLAR score

OBJECTIVES

To create a simple scoring system that can estimate 30-day mortality in patients requiring left-sided Impella implantation as standalone mechanical circulatory support (MCS).

METHODS

We retrospectively analysed 79 consecutive patients who required left-sided Impella MCS monotherapy. Regression analysis was used to elucidate significant associations between biochemical markers before Impella implantation and all-cause mortality at 30 days. Using these factors, a simple additive scoring system was created using a previously validated approach.

RESULTS

The BALLAR scoring system was created. Patients are assigned points based upon biochemical markers. These are summed and the final points tally provides an estimate of 30-day mortality. The points are assigned as follows: Lactate (mmol/l): ≤1.9: 0 points, 2-4.9: 1 Point, ≥5: 4 Points Creatinine Clearance (ml/min): ≤29.9: 6 points, 30-59.9: 4 points, 60-89.9: 1 point, ≥90: 0 points Serum Albumin (mmol/l): <25: 6 points, 25-34.9: 3 points, ≥35: 0 points Base Excess (mmol/L): < -2: 2 points, ≥-2: 0 points The total score can be used to estimate the probability of death at 30 days. A score less than 6 predicts a 30-day mortality of under 5%, whereas a score over 11 predicts a greater than 95% chance of death within 30 days.

CONCLUSION

Using this simple heuristic predicted 89% of 30-day deaths in our cohort. All the misclassifications were in the intermediate probability range (scores 5-11). This simple scoring system gives an effective estimate of the probability of death at 30 days in our cohort of patients.

From Euphoria to Dysphoria -Why do Cricketers Suffer from High Rates of Depression?

Cricketers suffer from higher rates of depression than both the general public and other sportsmen, as evidenced by the high suicide rates amongst retired test cricketers compared with age-matched controls. This is likely due to a complex array of psychosocial factors including the nature of sportsmen that play cricket, the unique nature of the sport, the duration of matches and hence the time away from support networks and the social situation of cricketers in the pre-professional era.

Complete resolution of acute pancreatitis-induced chylous ascites following transhepatic portal vein stenting

We introduce a case of a 73-year-old man who developed intractable chylous ascites due to portal vein compression as a result of peripancreatic inflammatory changes after acute biliary pancreatitis. After stenting the portal vein stenosis, the chylous ascites improved from requiring weekly paracentesis to requiring no drainage within 4 months of the procedure and at the 15-month follow-up. To our knowledge, it is the first case reported in the literature where portal vein stenting has successfully been used to treat pancreatitis-induced chylous ascites.

Diffusion tensor cardiovascular magnetic resonance detects altered myocardial microstructure in patients with acute st-elevation myocardial infarction

Background

Diffusion Tensor Cardiovascular Magnetic Resonance (DT-CMR) can quantify metrics of tissue integrity (mean diffusivity [MD] and fractional anisotropy [FA]) and changes in laminar microstructures (sheetlets), which reorientate from more wall-parallel in diastole (DIA) towards wall-perpendicular in systole (SYS) as the myocardium thickens, quantified by E2 angle [E2A]. Microstructural changes after STEMI may provide new insights into adverse LV remodelling and risk stratification.

Methods

In vivo DT-CMR was performed 3–5 days after PPCI for first presentation STEMI (N=19, mean age 57±9, 79% male). DT-CMR was acquired in 2 short-axes (SYS & DIA) using a STEAM-EPI sequence. 12 segment analysis of MD, FA, E2A and E2A mobility (ΔE2A = E2ASYS − E2ADIA) was performed. Infarct (INF) segments were defined as &gt;25% LGE, adjacent (ADJ, located contiguous to INF) and remote (REM, all other segments). Wilcoxon signed rank tests were used with threshold P&lt;0.017 (Bonferroni corrected).

Results

See Table.

MD in both SYS and DIA was significantly higher in INF and ADJ regions compared to REM. FA in both SYS and DIA was lower in the INF and ADJ compared to REM. E2ADIA was higher in INF, indicating a more wall-perpendicular orientation of sheetlets, compared to ADJ and REM zones. E2ASYS in INF was significantly reduced, indicating a more wall-parallel orientation of sheetlets, compared to ADJ and REM regions, resulting in significantly reduced sheetlet mobility (ΔE2A).

Conclusions

Microstructural changes can be detected after acute STEMI by in vivo DT-CMR. Zonal changes in MD and FA may suggest loss of barriers to water diffusion and altered cardiomyocyte organisation, respectively. We provide the first report of reduced sheetlet mobility after acute STEMI in INF. Ongoing work is evaluating the mechanisms and prognostic importance of altered sheetlet mobility after STEMI.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): British Heart Foundation Clinical Research Training Fellowship