Myocardial Perfusion Is Impaired and Relates to Cardiac Dysfunction in Patients With Atrial Fibrillation Both Before and After Successful Catheter Ablation

Metabolic remodelling in atrial fibrillation: manifestations, mechanisms and clinical implications

Atrial fibrillation (AF) is a continually growing health-care burden that often presents together with metabolic disorders, including diabetes mellitus and obesity. Current treatments often fall short of preventing AF and its adverse outcomes. Accumulating evidence suggests that metabolic disturbances can promote the development of AF through structural and electrophysiological remodelling, but the underlying mechanisms that predispose an individual to AF are aetiology-dependent, thus emphasizing the need for tailored therapeutic strategies to treat AF that target an individual's metabolic profile. AF itself can induce changes in glucose, lipid and ketone metabolism, mitochondrial function and myofibrillar energetics (as part of a process referred to as 'metabolic remodelling'), which can all contribute to atrial dysfunction. In this Review, we discuss our current understanding of AF in the setting of metabolic disorders, as well as changes in atrial metabolism that are relevant to the development of AF. We also describe the potential of available and emerging treatment strategies to target metabolic remodelling in the setting of AF and highlight key questions and challenges that need to be addressed to improve outcomes in these patients.

Prognostic impact of coronary microvascular dysfunction in patients with atrial fibrillation

BACKGROUND

Coronary microvascular dysfunction (CMD) is frequently observed in atrial fibrillation (AF), the most commonly sustained arrhythmia. Nevertheless, an in-depth prognostic significance of CMD in AF is lacking. We aimed to provide insight into the predictive impact of CMD assessed by a novel non-invasive coronary angiography-derived index of microcirculatory resistance (caIMR) for major adverse events (MACE) in AF patients.

METHOD

This study included patients with AF who underwent invasive coronary angiography due to suspected cardiac ischemia and did not exhibit obstructive epicardial coronary artery disease (≤50 % stenosis). The caIMR was prospectively evaluated, and the optimal cutoff value for predicting MACE was determined through ROC analysis.

RESULT

A total of 463 patients with AF were enrolled. During a median of 33 months of follow-up, 111 (23.97 %) patients had MACE endpoints. The best caIMR cutoff value was 39.28. In patients with MACE, both the mean caIMR and the prevalence of elevated caIMR (caIMR>39.28) were significantly higher compared to those without MACE. An elevated caIMR was linked to a higher risk of MACE (log-rank P < 0.001) and emerged as an independent predictor of clinical outcomes (HR: 4.029; 95 % CI: 2.529-6.418; P < 0.001). In addition, the risk of MACE was higher in high caIMR patients with non-paroxysmal AF (log-rank P < 0.001) and no catheter ablation (log-rank P < 0.001).

CONCLUSION

Elevated caIMR is common and showed a vital independent prognostic significance in AF patients. In addition to well-known risk factors, assessment of microvascular function can be a feasible approach for early prevention and a therapeutic target in AF patients.

Guiding early revascularization using [15O]H2O positron emission tomography myocardial perfusion imaging: impact of atrial fibrillation

AIMS

Myocardial perfusion imaging (MPI) using [15O]H2O positron emission tomography (PET) is used to guide the selection of patients with angina for invasive angiography and possible revascularization. Our study evaluated (i) whether atrial fibrillation (AF) reduces global hyperaemic myocardial blood flow (MBF) and (ii) whether [15O]H2O PET MPI effectively guides revascularization procedures for patients with ongoing AF.

METHODS AND RESULTS

We prospectively recruited 346 patients with angina and persistent or paroxysmal AF referred for baseline/hyperaemic [15O]H2O PET MPI. The primary outcome was revascularization within 3 months of MPI. In the analyses, patients were divided into four groups based on whether they had ongoing AF or sinus rhythm (SR) and whether they had previously documented coronary artery disease (CAD) or not. Thus, four groups were compared: SR-noCAD, AF-noCAD, SR-CAD, and AF-CAD. Hyperaemic MBF was affected by both ongoing AF and prior CAD [MBF (mL/min/g): 2.82 (SR-noCAD) vs. 2.12 (AF-noCAD) vs. 2.22 (SR-CAD) vs. 1.80 (AF-CAD), two-way analysis of variance P < 0.0001]. In multiple linear regression, ongoing AF was independently associated with reduced hyperaemic MBF. Every 0.1 mL/min/g decrease in hyperaemic MBF was associated with a 23% increase in odds of early revascularization. Receiver operating characteristic (ROC) analysis of vessel-specific hyperaemic MBF to predict early revascularization yielded the following areas under the ROC curve: SR-noCAD: 0.95 (P < 0.0001); AF-noCAD: 0.79 (P < 0.0001); SR-CAD: 0.78 (P < 0.0001); and AF-CAD: 0.88 (P < 0.0001).

CONCLUSION

Ongoing AF is associated with 19-25% reduced global hyperaemic MBF as measured by [15O]H2O MPI PET. Regardless, vessel-specific hyperaemic MBF still predicts early revascularization in patients with AF.

The ratio of cytochrome c oxidase subunit 4 isoform 4I1 and 4I2 mRNA is changed in permanent atrial fibrillation

AIMS

The conditions of hypoxia are suggested to induce permanent atrial fibrillation (AF). The regulation of COX4I2 and COX4I1 depends on oxygen availability in tissues. A role of COX4I2 in the myocardium of AF patients is supposed for pathogenesis of AF and subsequent alterations in the electron transfer chain (ETC) under hypoxia.

METHODS AND RESULTS

In vitro, influence of hypoxia on HeLa 53 cells was studied and elevated parts of COX 4I2 were confirmed. Myocardial biopsies were taken ex vivo from the patients' Right Atria with SR (n = 31) and AF (n = 11), respectively. RT- PCR for mRNA expresson, mitochondrial respiration by polarography and the protein content of cytochrome c oxidase (CytOx) subunit 4I1 and CytOx subunit 4I2 by ELISA were studied. Clinical data were correlated to the findings of gene expressions in parallel. Patients with permanent AF had a change in isoform 4I2/4I1 expression along with a decrease of isoform COX 4I1 expression. The 4I2/4I1 ratio of mRNA expression was increased from 0.630 to 1.058 in comparison. However, the protein content of CytOx subunit 4 was much lower in the AF group, whereas the respiration/units enzyme activity in both groups remained the same.

CONCLUSIONS

This study describes a possible molecular correlate for the development of AF. Due to the known functional significance of COX 4I2, mitochondrial dysfunction can be assumed as a part of the pathogenesis of AF.

Coronary microvascular dysfunction, arrythmias, and sudden cardiac death: A literature review

The coronary vascular system has a unique structure and function that is adaptive to myocardial demand. It is composed of a continuous network of vessels receding in size from epicardial arteries to the microvascular circulation. Failure to meet myocardial demand results in ischemia, angina, and adverse myocardial outcomes. It is evident that 50 % of patients with angina have a non-obstructive coronary disease and 66 % of these patients have coronary microvascular dysfunction (CMD). The impact of CMD on the atria and ventricles is exhibited through its association with atrial fibrillation and distortion of ventricular repolarization. Ultimately, this influence increases the risk of mortality, morbidity, and sudden cardiac arrest. CMD serves as an independent risk for atrial fibrillation, increases ventricular electrical inhomogeneity, and contributes to the progression of cardiac disease. The underlying pathogenesis may be attributed to oxidative stress evident through reactive oxygen species, impaired vasoactive function, and structural disorders such as fibrotic changes. Myocardial ischemia, brought about by a demand-supply mismatch in CMD, may create a milieu for ventricular arrythmia and sudden cardiac arrest through distortion of ventricular repolarization parameters such as QT dispersion and corrected QT dispersion.

Pulsed Field Ablation for Atrial Fibrillation: Mechanisms, Advantages, and Limitations

Pulsed field ablation with irreversible electroporation for the treatment of atrial fibrillation involves tissue-specific and non-thermal energy-induced cell necrosis, which helps avoid complications, such as pulmonary vein stenosis, atrial collateral tissue damage, and extensive atrial structural damage, often encountered with traditional thermal ablation. In existing clinical trials, pulsed field ablation has shown excellent effects on pulmonary vein isolation in patients with paroxysmal and persistent atrial fibrillation. Pulsed field ablation is easy, simple, and quick and can reduce iatrogenic injury. Therefore, the application of pulsed field ablation technology in the treatment of atrial fibrillation has a promising future. Notably, the adjustment of parameters in pulsed field ablation with different ablation catheter systems can strongly affect the area and depth of the necrotic myocardium, which greatly affects the likelihood of atrial fibrillation recurrence and incidence of adverse complications after ablation. In this paper, we review the mechanisms, advantages, and limitations of pulsed field ablation based on the results of a series of previous studies and provide ideas and directions for future research.

The worsening effect of paroxysmal atrial fibrillation on left ventricular function and deformation in type 2 diabetes mellitus patients: a 3.0 T cardiovascular magnetic resonance feature tracking study

BACKGROUND

Atrial fibrillation (AF) has been linked to an increased risk of cardiovascular death, overall mortality and heart failure in patients with type 2 diabetes mellitus (T2DM). The present study investigated the additive effects of paroxysmal AF on left ventricular (LV) function and deformation in T2DM patients with or without AF using the cardiovascular magnetic resonance feature tracking (CMR-FT) technique.

METHODS

The present study encompassed 225 T2DM patients differentiated by the presence or absence of paroxysmal AF [T2DM(AF+) and T2DM(AF-), respectively], along with 75 age and sex matched controls, all of whom underwent CMR examination. LV function and global strains, including radial, circumferential and longitudinal peak strain (PS), as well as peak systolic and diastolic strain rates (PSSR and PDSR, respectively), were measured and compared among the groups. Multivariable linear regression analysis was used to examine the factors associated with LV global strains in patients with T2DM.

RESULTS

The T2DM(AF+) group was the oldest, had the highest LV end‑systolic volume index, lowest LV ejection fraction and estimated glomerular filtration rate compared to the control and T2DM(AF-) groups, and presented a shorter diabetes duration and lower HbA1c than the T2DM(AF-) group. LV PS-radial, PS-longitudinal and PDSR-radial declined successively from controls through the T2DM(AF-) group to the T2DM(AF+) group (all p < 0.001). Compared to the control group, LV PS-circumferential, PSSR-radial and PDSR-circumferential were decreased in the T2DM(AF+) group (all p < 0.001) but preserved in the T2DM(AF-) group. Among all clinical indices, AF was independently associated with worsening LV PS-longitudinal (β = 2.218, p < 0.001), PS-circumferential (β = 3.948, p < 0.001), PS-radial (β = - 8.40, p < 0.001), PSSR-radial and -circumferential (β = - 0.345 and 0.101, p = 0.002 and 0.014, respectively), PDSR-radial and -circumferential (β = 0.359 and - 0.14, p = 0.022 and 0.003, respectively).

CONCLUSIONS

In patients with T2DM, the presence of paroxysmal AF further exacerbates LV function and deformation. Proactive prevention, regular detection and early intervention of AF could potentially benefit T2DM patients.

Coronary microvascular dysfunction and myocardial infarction with non-obstructive coronary arteries: Where do we stand?

In the past decade, scientific and clinical research has provided a translational perspective on myocardial infarction (MI) with non-obstructive coronary arteries (MINOCA). MINOCA is characterized by clinical documentation of an acute MI but angiography shows no significant coronary artery obstruction (stenosis <50%). The prevalence of MINOCA is estimated to range from approximately 6 to 10% among MI patients, and those with this condition have a poor prognosis, experiencing high rates of mortality, rehospitalization, and socioeconomic burden. MINOCA represents a major unmet need in cardiovascular medicine, with uncertain clinical management. It is a complex condition that can be caused by various factors, including atherosclerosis, plaque rupture, coronary vasospasm, and microvascular dysfunction. Effective management of MINOCA depends on identifying the underlying mechanism of the infarction, thus a systematic diagnostic approach is recommended. Contemporary data shows that a significant number of patients exhibit structural and functional abnormalities in coronary microcirculation, which is referred to as coronary microvascular dysfunction (CMD). CMD plays a crucial role in patients with signs and symptoms of myocardial ischemia and non-obstructive coronary artery stenosis, including MINOCA. Furthermore, conducting a thorough evaluation of coronary function can have significant prognostic and therapeutic implications, since personalized patient management strategies based on this assessment have been shown to improve symptoms and prognosis. Therefore, an accurate and timely diagnosis of CMD is essential for effective patient management, which can be achieved through various invasive and non-invasive methods. This review will discuss the pathophysiological understanding, current diagnostic techniques, and management strategies of patients with MINOCA and CMD.

Particularities of coronary physiology in patients with atrial fibrillation: insights from combined pressure and flow indices measurements

Background

Symptoms suggestive of myocardial ischemia are frequently encountered in patients with atrial fibrillation (AF) even in the absence of obstructive coronary artery disease. Nevertheless, an in-depth characterisation of coronary physiology in patients with AF is currently lacking.

Objectives

We aim to provide an insight into the characteristics of coronary physiology in AF, by performing simultaneous invasive measurements of coronary flow- and pressure- indices in a real-life population of patients with AF and indication of coronary angiography.

Methods

This is a prospective open label study including patients with permanent or persistent AF and indication of coronary angiography showing intermediate coronary stenosis requiring routine physiological assessment (n = 18 vessels from 14 patients). We measured FFR (fractional flow reserve), and Doppler-derived coronary flow indices, including CFR (coronary flow reserve) and HMR (hyperaemic microvascular resistance).

Results

From the analysed vessels, 18/18 vessels (100%) presented a pathological CFR (<2.5), indicative of coronary microvascular dysfunction (CMD), and 3/18 (17%) demonstrated obstructive epicardial coronary disease (FFR ≤ 0.8). A large proportion of vessels (15/18; 83%) showed discordant FFR/CFR with preserved FFR and low CFR. 47% of the coronary arteries in patients with AF and non-obstructive epicardial coronary disease presented structural CMD (HMR ≥ 2.5 mmHg/cm/s), and were associated with high BMR and an impaired response to adenosine. Conversely, vessels from patients with AF and non-obstructive epicardial coronary disease with functional CMD (HMR < 2.5 mmHg/cm/s) showed higher bAPV. The permanent AF subpopulation presented increased values of HMR and BMR compared to persistent AF, while structural CMD was more often associated with persistent symptoms at 3 months, taking into account the limited sample size of our study.

Conclusion

Our findings highlight a systematically impaired CFR in patients with AF even in the absence of obstructive epicardial coronary disease, indicative of CMD. In addition, patients with AF presented more prevalent structural CMD (HMR ≥ 2.5 mmHg/cm/s), characterized by reduced hyperaemic responses to adenosine, possibly interfering with the FFR assessment.

Cardiac Magnetic Resonance Imaging-Derived Left Atrial Characteristics in Relation to Atrial Fibrillation Detection in Patients With an Implantable Cardioverter-Defibrillator

Background Among patients with an implantable cardioverter-defibrillator, a high prevalence of atrial fibrillation (AF) is present. Identification of AF predictors in this patient group is of clinical importance to initiate appropriate preventive therapeutic measures to reduce the risk of AF-related complications. This study assesses whether cardiac magnetic resonance imaging-derived atrial characteristics are associated with AF development in patients with a dual-chamber implantable cardioverter-defibrillator or cardiac resynchronization therapy defibrillator, as detected by the cardiac implantable electronic device. Methods and Results This single-center retrospective study included 233 patients without documented AF history at the moment of device implantation (dual-chamber implantable cardioverter-defibrillator [63.5%] or cardiac resynchronization therapy defibrillator [36.5%]). All patients underwent cardiac magnetic resonance imaging before device implantation. Cardiac magnetic resonance-derived features of left atrial (LA) remodeling were evaluated in all patients. Detection of AF episodes was based on cardiac implantable electronic device interrogation. During a median follow-up of 6.1 years, a newly diagnosed AF episode was detected in 88 of the 233 (37.8%) patients with an ICD. In these patients, increased LA volumes and impaired LA function (LA emptying fraction and LA strain) were found as compared with patients without AF during follow-up. However, a significant association was only found in patients with dilated cardiomyopathy and not in patients with ischemic cardiomyopathy. Conclusions LA remodeling characteristics were associated with development of AF in patients with dilated cardiomyopathy but not patients with ischemic cardiomyopathy, suggesting different mechanisms of AF development in ischemic cardiomyopathy and dilated cardiomyopathy. Assessment of LA remodeling before device implantation might identify high-risk patients for AF.

Myocardial Blush Grade Predicts Postoperative Atrial Fibrillation following Mitral Valve Replacement: A Novel Perspective

Background: Atrial fibrillation (AF) remains the most common arrhythmia following mitral valve surgery. Although numerous clinical and laboratory indicators and possible mechanisms of postoperative AF (PoAF) have been described, the role of microvascular dysfunction in pathogenesis has not been assessed. We aimed to evaluate the association between microvascular dysfunction and PoAF in patients undergoing isolated mitral valve replacement. Methods: 188 patients undergoing mitral valve replacement were included in this retrospective study. Demographic characteristics of the patients were recorded. Angiographic assessment of microvascular perfusion was performed using the myocardial blush grading technique for each patient. Univariate and multivariate logistic regression analyses were utilized to determine predictors of PoAF. Results: Of 188 patients (56.69 ± 8.9 years, 39.4% male) who underwent mitral valve replacement, 64 (34%) patients developed PoAF. In the PoAF group, a lower basal hemoglobin level (12.64 ± 0.89 vs. 14.46 ± 0.91 g/dL; p < 0.001), a higher left atrial diameter [5.9 (5.2-6.47) vs. 4.9 (4.5-5.8) cm; p < 0.001], and a lower total blush score (TBS) (8.33 ± 0.84 vs. 8.9 ± 0.31; p < 0.001) were detected. Multivariate logistic regression analysis revealed that preoperative LA diameter (OR:2.057; 95% CI: 1.166-3.63; p = 0.013), preoperative hemoglobin (OR:0.12; 95% CI: 0.058-0.245; p < 0.001), and abnormal TBS (OR:15.1; 95% CI: 1.602-142.339; p = 0.018) were independent predictors of PoAF. Conclusions: Our findings demonstrated that TBS at the preoperative period was an independent predictor of PoAF in patients undergoing isolated mitral valve replacement.

Coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance imaging of coronary sinus: a meta-analysis

BACKGROUND

Phase-contrast cine cardiovascular magnetic resonance (CMR) of the coronary sinus has emerged as a non-invasive method for measuring coronary sinus blood flow and coronary flow reserve (CFR). However, its clinical utility has not yet been established. Here we performed a meta-analysis to clarify the clinical value of CMR-derived CFR in various cardiovascular diseases.

METHODS

An electronic database search was performed of PubMed, Web of Science Core Collection, Cochrane Advanced Search, and EMBASE. We compared the CMR-derived CFR of various cardiovascular diseases (stable coronary artery disease [CAD], hypertrophic cardiomyopathy [HCM], dilated cardiomyopathy [DCM]) and control subjects. We assessed the prognostic value of CMR-derived CFR for predicting major adverse cardiac events (MACE) in patients with stable CAD.

RESULTS

A total of 47 eligible studies were identified. The pooled CFR from our meta-analysis was 3.48 (95% confidence interval [CI], 2.98-3.98) in control subjects, 2.50 (95% CI, 2.38-2.61) in stable CAD, 2.01 (95% CI, 1.70-2.32) in cardiomyopathies (HCM and DCM). The meta-analysis showed that CFR was significantly reduced in stable CAD (mean difference [MD] = -1.48; 95% CI, -1.78 to -1.17; p < 0.001; I2 = 0%; p for heterogeneity = 0.33), HCM (MD = -1.20; 95% CI, -1.63 to -0.77; p < 0.001; I2 = 0%; p for heterogeneity = 0.49), and DCM (MD = -1.53; 95% CI, -1.93 to -1.13; p < 0.001; I2 = 0%; p for heterogeneity = 0.45). CMR-derived CFR was an independent predictor of MACE for patients with stable CAD (hazard ratio = 0.52 per unit increase; 95% CI, 0.37-0.73; p < 0.001; I2 = 84%, p for heterogeneity < 0.001).

CONCLUSIONS

CMR-derived CFR was significantly decreased in cardiovascular diseases, and a decreased CFR was associated with a higher occurrence of MACE in patients with stable CAD. These results suggest that CMR-derived CFR has potential for the pathological evaluation of stable CAD, cardiomyopathy, and risk stratification in CAD.

Ischemia with Nonobstructive Coronary Artery Disease and Atrial Cardiomyopathy-Two Sides of the Same Story?

Ischemia with nonobstructive coronary artery disease (INOCA) is increasingly recognized as a significant cause of angina, myocardial remodeling, and eventually heart failure (HF). Coronary microvascular dysfunction (CMD) is a major endotype of INOCA, and it is caused by structural and functional alterations of the coronary microcirculation. At the same time, atrial cardiomyopathy (ACM) defined by structural, functional, and electrical atrial remodeling has a major clinical impact due to its manifestations: atrial fibrillation (AF), atrial thrombosis, stroke, and HF symptoms. Both these pathologies share similar risk factors and have a high comorbidity burden. CMD causing INOCA and ACM frequently coexist. Thus, questions arise whether there is a potential link between these pathologies. Does CMD promote AF or the reverse? Which are the mechanisms that ultimately lead to CMD and ACM? Are both part of a systemic disease characterized by endothelial dysfunction? Lastly, which are the therapeutic strategies that can target endothelial dysfunction and improve the prognosis of patients with CMD and ACM? This review aims to address these questions by analyzing the existing body of evidence, offering further insight into the mechanisms of CMD and ACM, and discussing potential therapeutic strategies.

Case Report: Pulmonary Vein Isolation as a Tailored Treatment for Recurrent Ventricular Tachycardia During Hemodialysis in a Patient With Right Coronary Artery Chronic Total Occlusion

Background

Catheter ablation of the ventricular substrate can reduce ventricular tachycardia (VT) recurrence and mortality in an electrical storm (ES). However, identification and specific treatment of plausible triggers is mandatory and may lead to the resolution of ES.

Objective

This case presentation seeks to exemplify how pulmonary vein isolation (PVI) may represent a tailored treatment of ES in cases of ventricular substrate, which only becomes arrhythmogenic during high-rate episodes of paroxysmal atrial fibrillation (PAF).

Results

A 54-year-old male with a history of inferior myocardial infarction (MI) and long-term hemodialysis was referred for repetitive implantable cardioverter-defibrillator (ICD) shocks for apparently scar-related monomorphic VT episodes preceded by PAF initiation strictly during hemodialysis. He had recently undergone ICD implantation for similar episodes of ES preceded by the rapid-ventricular response (RVR) PAF during hemodialysis. The patient had no other history of VTs. Electrocardiogram (EKG) changes occurred exclusively during PAF and suggested functional myocardial ischemia. Coronary angiography demonstrated isolated right coronary artery (RCA) chronic total occlusion (CTO). Cardiac magnetic resonance demonstrated RCA-territory residual myocardial viability and mild LV systolic dysfunction. Surgical revascularization was not feasible due to a history of bilateral above-the-knee post-traumatic amputation and severe calcification of internal mammary (IMA) and radial arteries. Subsequent CTO-percutaneous coronary intervention attempt was unsuccessful. The difficulty of assessing LV-substrate ablation end-points due to the “functional” character of the substrate, which only became arrhythmogenic during hemodialysis-related PAF, was considered. Consequently, PVI was performed rather than VT/VF substrate ablation. Twelve months after PVI, the patient remains free of PAF and VT/VF despite chronic hemodialysis sessions.

Conclusion

The ES episodes can be triggered by situational factors, such as RVR-PAF and functional ischemia, during hemodialysis in patients with CTO with otherwise no episodes of VT. Tailored treatment of such factors may lead to long-term VT freedom.

The impact of atrial fibrillation and stroke risk factors on left atrial blood flow characteristics

AIMS

Altered left atrial (LA) blood flow characteristics account for an increase in cardioembolic stroke risk in atrial fibrillation (AF). Here, we aimed to assess whether exposure to stroke risk factors is sufficient to alter LA blood flow even in the presence of sinus rhythm (SR).

METHODS AND RESULTS

We investigated 95 individuals: 37 patients with persistent AF, who were studied before and after cardioversion [Group 1; median CHA2DS2-VASc = 2.0 (1.5-3.5)]; 35 individuals with no history of AF but similar stroke risk to Group 1 [Group 2; median CHA2DS2-VASc = 3.0 (2.0-4.0)]; and 23 low-risk individuals in SR [Group 3; median CHA2DS2-VASc = 0.0 (0.0-0.0)]. Cardiac function and LA flow characteristics were evaluated using cardiac magnetic resonance. Before cardioversion, Group 1 displayed impaired left ventricular (LV) and LA function, reduced LA flow velocities and vorticity, and a higher normalized vortex volume (all P < 0.001 vs. Groups 2 and 3). After restoration of SR at ≥4-week post-cardioversion, LV systolic function and LA flow parameters improved significantly (all P < 0.001 vs. pre-cardioversion) and were no longer different from those in Group 2. However, in the presence of SR, LA flow peak and mean velocity, and vorticity were lower in Groups 1 and 2 vs. Group 3 (all P < 0.01), and were associated with impaired LA emptying fraction (LAEF) and LV diastolic dysfunction.

CONCLUSION

Patients at moderate-to-high stroke risk display altered LA flow characteristics in SR in association with an LA myopathic phenotype and LV diastolic dysfunction, regardless of a history of AF.

Long-term prognostic value of vasodilator stress cardiac magnetic resonance in patients with atrial fibrillation

AIMS

Although the prevalence of coronary artery disease (CAD) is high among patients with atrial fibrillation (AF), studies on stress perfusion cardiac magnetic resonance (CMR) imaging frequently exclude patients with AF, and its prognostic and diagnostic value in high-risk patients with suspected or known CAD remains unclear.

METHODS AND RESULTS

In this longitudinal cohort study, we included 164 consecutive patients with AF during vasodilator perfusion CMR. Diagnostic value was evaluated regarding invasive coronary angiography in a subset of patients. We targeted a follow-up of >5 years and used CMR results as stratification, and the primary outcome was major adverse cardiac events [MACE, cardiovascular (CV) death and myocardial infarction (MI)]. Secondary outcomes included late coronary revascularization or stroke and the components of the primary outcome. Of the whole cohort (73.8% male, mean age 72.2 years ± 7.8 SD), 99.4% were successfully scanned (163/164 patients). Median CHA2DS2-VASc score was 4 [interquartile range (IQR) 3-5], and median 10-year risk for CV events based on SMART risk score was high (24%, IQR 16-32%). Thirty-two patients (19.6%) presented with ischaemia and 52 patients (31.9%) with late gadolinium enhancement (LGE). A combination of LGE and inducible ischaemia was present in 20 patients (12.3%). Diagnostic accuracy was 86.2% [confidence interval (CI) 68.3-96.1%]. The median follow-up was 6.6 years (IQR 3.6-7.8). Ischaemia in vasodilator perfusion CMR was significantly associated with the occurrence of MACE [P < 0.01; hazard ratio (HR) 2.65, CI 1.39-5.08], as well as LGE (P = 0.03; 1.74, CI 1.07-3.64) and the combination of both (P < 0.01; HR 2.67, CI 1.59-5.62). After adjustment by age, left ventricular ejection fraction, and the presence of diabetes, ischaemia in vasodilator perfusion CMR remained significantly associated with the occurrence of MACE (2.10, CI 1.08-4.10; P = 0.03). In secondary endpoint analysis, there was a significant association of ischaemia in CMR with CV death (P < 0.05; HR 1.93, CI 0.95-3.9) and MI (P < 0.01; HR 13, CI 1.35-125.4), while no significant association was found regarding the occurrence of revascularization (P = 0.45; HR 1.43, CI 0.57-3.58) or stroke (P = 0.99; HR 0.99, CI 0.21-2.59).

CONCLUSIONS

Vasodilator stress perfusion CMR demonstrated an excellent diagnostic and significant prognostic value at long-term follow-up in high-risk patients with persistent AF and suspected or known CAD.

Hyperemic myocardial blood flow in patients with atrial fibrillation before and after catheter ablation: A dynamic stress CT perfusion study

BACKGROUND

Atrial fibrillation (AF) patients without coronary artery stenosis often show clinical evidence of ischemia. However myocardial perfusion in AF patients has been poorly studied. The purposes of this study were to investigate altered hyperemic myocardial blood flow (MBF) in patients with AF compared with risk-matched controls in sinus rhythm (SR), and to evaluate hyperemic MBF before and after catheter ablation using dynamic CT perfusion.

METHODS

Hyperemic MBF was quantified in 87 patients with AF (44 paroxysmal, 43 persistent) scheduled for catheter ablation using dynamic CT perfusion, and compared with hyperemic MBF in 87 risk-matched controls in SR. Follow-up CT after ablation was performed in 49 AF patients.

RESULTS

Prior to ablation, hyperemic MBF of patients in AF during the CT (1.29 ± 0.34 ml/mg/min) was significantly lower than in patients in SR (1.49 ± 0.26 ml/g/min, p = 0.002) or matched controls (1.65 ± 0.32 ml/g/min, p < 0.001); no significant difference was seen between patients in SR during the CT and matched controls (vs. 1.50 ± 0.31 ml/g/min, p = 0.815). In patients in AF during the pre-ablation CT (n = 24), hyperemic MBF significantly increased after ablation from 1.30 ± 0.35 to 1.53 ± 0.17 ml/g/min (p = 0.004); whereas in patients in SR during the pre-ablation CT (n = 25), hyperemic MBF did not change significantly after ablation (from 1.46 ± 0.26 to 1.49 ± 0.27 ml/g/min, p = 0.499).

CONCLUSION

In the current study using stress perfusion CT, hyperemic MBF in patients with AF during pre-ablation CT was significantly lower than that in risk-matched controls, and improved significantly after restoration of SR by catheter ablation, indicating that MBF abnormalities in AF patients are caused primarily by AF itself.

Left atrial 4D flow cardiovascular magnetic resonance: a reproducibility study in sinus rhythm and atrial fibrillation

BACKGROUND

Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) allows sophisticated quantification of left atrial (LA) blood flow, and could yield novel biomarkers of propensity for intra-cardiac thrombus formation and embolic stroke. As reproducibility is critically important to diagnostic performance, we systematically investigated technical and temporal variation of LA 4D flow in atrial fibrillation (AF) and sinus rhythm (SR).

METHODS

Eighty-six subjects (SR, n = 64; AF, n = 22) with wide-ranging stroke risk (CHA2DS2VASc 0-6) underwent LA 4D flow assessment of peak and mean velocity, vorticity, vortex volume, and stasis. Eighty-five (99%) underwent a second acquisition within the same session, and 74 (86%) also returned at 30 (27-35) days for an interval scan. We assessed variability attributable to manual contouring (intra- and inter-observer), and subject repositioning and reacquisition of data, both within the same session (same-day scan-rescan), and over time (interval scan). Within-subject coefficients of variation (CV) and bootstrapped 95% CIs were calculated and compared.

RESULTS

Same-day scan-rescan CVs were 6% for peak velocity, 5% for mean velocity, 7% for vorticity, 9% for vortex volume, and 10% for stasis, and were similar between SR and AF subjects (all p > 0.05). Interval-scan variability was similar to same-day scan-rescan variability for peak velocity, vorticity, and vortex volume (all p > 0.05), and higher for stasis and mean velocity (interval scan CVs of 14% and 8%, respectively, both p < 0.05). Longitudinal changes in heart rate and blood pressure at the interval scan in the same subjects were associated with significantly higher variability for LA stasis (p = 0.024), but not for the remaining flow parameters (all p > 0.05). SR subjects showed significantly greater interval-scan variability than AF patients for mean velocity, vortex volume, and stasis (all p < 0.05), but not peak velocity or vorticity (both p > 0.05).

CONCLUSIONS

LA peak velocity and vorticity are the most reproducible and temporally stable novel LA 4D flow biomarkers, and are robust to changes in heart rate, blood pressure, and differences in heart rhythm.

Changes in Subendocardial Viability Ratio in Traumatic Brain Injury Patients

Background: Traumatic brain injury (TBI) is often associated with cardiac dysfunction, which is a consequence of the brain-heart cross talk. The subendocardial viability ratio (SEVR) is an estimate of myocardial perfusion. The aim of this study was to analyze changes in the SEVR in patients with severe TBI without previous cardiac diseases. Methods: Adult patients treated for severe TBI with a Glasgow coma score <8 were studied. Pressure waveforms were obtained by a high-fidelity tonometer in the radial artery for SEVR calculation at five time points: immediately after admission to the intensive care unit and 24, 48, 72, and 96 h after admission. SEVRs and other clinically important parameters were analyzed in patients who survived and did not survive after 28 days of treatment, as well as in patients who underwent decompressive craniectomy (DC). Results: A total of 64 patients (16 females and 48 males) aged 18-64 years were included. Fifty patients survived and 14 died. DC was performed in 23 patients. SEVRs decreased 24 h after admission in nonsurvivors (p < 0.05) and after 48 h in survivors (p < 0.01) and its values were significantly lower in nonsurvivors than in survivors at 24, 72, and 96 h from admission (p < 0.05). The SEVR increased following DC (p < 0.05). Conclusions: A decreased SEVR is observed in TBI patients. Surgical decompression increases the SEVR, indicating improvement in coronary microvascular perfusion. The results of our study seem to confirm that brain injury affects myocardium function.

Impaired coronary flow reserve evaluated by phase-contrast cine magnetic resonance imaging in patients with atrial fibrillations

Myocardial perfusion and perfusion reserve are diminished in patients with atrial fibrillation (AF). Phase-contrast (PC) cine magnetic resonance imaging (MRI) of the coronary sinus serves as a non-invasive means of quantifying coronary flow reserve (CFR) without any radioactive tracer. The present study aimed to evaluate the utility of PC cine MRI of the coronary sinus for assessing decreased CFR in patients with AF. We studied 362 patients with known or suspected coronary artery disease (CAD) [age 72 ± 9 years; 267 (74%) male; 90 (25%) had AF] and 20 age- and gender-matched control subjects [age 72 ± 9 years, 14 (70%) male]. Using a 1.5-T MR scanner and cardiac coils, blood flow of the coronary sinus (CBF) was quantified by PC cine MRI. CFR was calculated as CBF during adenosine triphosphate infusion divided by CBF at rest. CFR was significantly lower in patients with AF than in those without AF among all patients (n = 362) (2.45 ± 0.42 vs. 2.71 ± 0.58, p < 0.001), in patients with known CAD (n = 155) (2.40 ± 0.46 vs. 2.72 ± 0.58, p = 0.002), and in those with suspected CAD (n = 207) (2.49 ± 0.40 vs. 2.72 ± 0.59, p = 0.007). Significant differences in CFR were found between controls and patients without AF (3.12 ± 0.52 vs. 2.71 ± 0.58, p < 0.001). AF was independently associated with CFR in both known CAD patients [β = - 0.248, 95% confidence interval (CI): - 0.561 to - 0.119, p = 0.003) and suspected CAD patients (β =  - 0.154, 95% CI - 0.353 to - 0.034, p = 0.018). The presence of AF was related to impaired CFR in both known and suspected CAD patients. PC cine MRI of the coronary sinus can be useful for detecting impaired CFR in patients with AF.

Association of White Matter Hyperintensities and Cardiovascular Disease: The Importance of Microcirculatory Disease

Cardiac and cerebrovascular diseases are currently the leading causes of mortality and disability worldwide. Both the heart and brain display similar vascular anatomy, with large conduit arteries running on the surface of the organ providing tissue perfusion through an intricate network of penetrating small vessels. Both organs rely on fine tuning of local blood flow to match metabolic demand. Blood flow regulation requires adequate functioning of the microcirculation in both organs, with loss of microvascular function, termed small vessel disease (SVD) underlying different potential clinical manifestations. SVD in the heart, known as coronary microvascular dysfunction, can cause chronic or acute myocardial ischemia and may lead to development of heart failure. In the brain, cerebral SVD can cause an acute stroke syndrome known as lacunar stroke or more subtle pathological alterations of the brain parenchyma, which may eventually lead to neurological deficits or cognitive decline in the long term. Coronary microcirculation cannot be visualized in vivo in humans, and functional information can be deduced by measuring the coronary flow reserve. The diagnosis of cerebral SVD is largely based on brain magnetic resonance imaging, with white matter hyperintensities, microbleeds, and brain atrophy reflecting key structural changes. There is evidence that such structural changes reflect underlying cerebral SVD. Here, we review interactions between SVD and cardiovascular risk factors, and we discuss the evidence linking cerebral SVD with large vessel atheroma, atrial fibrillation, heart failure, and heart valve disease.

Clinical features, sex differences and outcomes of myocardial infarction with nonobstructive coronary arteries: a registry analysis

INTRODUCTION

Clinical characteristics and outcomes of patients diagnosed with myocardial infarction (MI) with nonobstructive coronary arteries (MINOCA) remain largely unknown. Furthermore, we do not yet understand if women with MINOCA have worse outcomes similar to what has historically been observed with MI. The aims of the current study were to evaluate the (1) incidence of MINOCA in patients presenting with MI, (2) compare in-hospital outcomes of MINOCA and obstructive atherosclerotic coronary artery disease MI (OACD-MI), and (3) comparison of in-hospital clinical outcomes of patients with MINOCA stratified by sex.

METHODS AND RESULTS

In this observational study, we combined data from two large university hospitals from Canada and Australia. Clinical characteristics and in-hospital outcomes of MINOCA and OACD-MI were analyzed by matching these patients in a 1:1 ratio after selecting patients with OACD-MI by systematic random sampling. Clinical characteristics associated with MINOCA were identified through multivariate logistic regression. Primary outcome of interest was net adverse cardiovascular events (NACE) defined as death, heart failure, stroke, and major bleeding. The incidence rate of MINOCA was 9.5%. Women, absence of traditional cardiac risk factors, and absence of ST-deviations on ECG were associated with diagnosis of MINOCA on angiography. NACE (P = 0.0001), death (P = 0.019), stroke (P = 0.002), and heart failure (P = 0.001) were significantly lower in patients with MINOCA. Subgroup analysis of women and men diagnosed with MINOCA revealed similar in-hospital outcomes.

CONCLUSION

The incidence of MINOCA was 9.5%. Compared to OACD-MI, patients with MINOCA have less cardiac risk factors. In-hospital outcomes of patients diagnosed with MINOCA were better than OACD-MI.

Mechanisms of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia, currently affecting over 33 million individuals worldwide, and its prevalence is expected to more than double over the next 40 years. AF is associated with a twofold increase in premature mortality, and important major adverse cardiovascular events such as heart failure, severe stroke and myocardial infarction. Significant effort has been made over a number of years to define the underlying cellular, molecular and electrophysiological changes that predispose to the induction and maintenance of AF in patients. Progress has been limited by the realisation that AF is a complex arrhythmia that can be the end result of various different pathophysiological processes, with significant heterogeneity between individual patients (and between species). In this focused Review article, we aim to succinctly summarise for the non-specialist the current state of knowledge regarding the mechanisms of AF. We address all aspects of pathophysiology, including the basic electrophysiological and structural changes within the left atrium, the genetics of AF and the links to comorbidities and wider systemic and metabolic perturbations that may be upstream contributors to development of AF. Finally, we outline the translational implications for current and future rhythm control strategies in patients with AF.

Impaired coronary blood flow at higher heart rates during atrial fibrillation: Investigation via multiscale modelling

BACKGROUND

Different mechanisms have been proposed to relate atrial fibrillation (AF) and coronary flow impairment, even in absence of relevant coronary artery disease (CAD). However, the underlying hemodynamics remains unclear. Aim of the present work is to computationally explore whether and to what extent ventricular rate during AF affects the coronary perfusion.

METHODS

AF is simulated at different ventricular rates (50, 70, 90, 110, 130 bpm) through a 0D-1D multiscale validated model, which combines the left heart-arterial tree together with the coronary circulation. Artificially-built RR stochastic extraction mimics the in vivo beating features. All the hemodynamic parameters computed are based on the left anterior descending (LAD) artery and account for the waveform, amplitude and perfusion of the coronary blood flow.

RESULTS

Alterations of the coronary hemodynamics are found to be associated either to the heart rate increase, which strongly modifies waveform and amplitude of the LAD flow rate, and to the beat-to-beat variability. The latter is overall amplified in the coronary circulation as HR grows, even though the input RR variability is kept constant at all HRs.

CONCLUSIONS

Higher ventricular rate during AF exerts an overall coronary blood flow impairment and imbalance of the myocardial oxygen supply-demand ratio. The combined increase of heart rate and higher AF-induced hemodynamic variability lead to a coronary perfusion impairment exceeding 90-110 bpm in AF. Moreover, it is found that coronary perfusion pressure (CPP) is no longer a good measure of the myocardial perfusion for HR higher than 90 bpm.