Left ventricular ejection fraction for the risk stratification of sudden cardiac death: friend or foe?

More than 450000 Americans die suddenly each year from sustained ventricular tachycardia or fibrillation. A correct identification of these patients is crucial for a rational clinical management, because the demonstrated effectiveness of implantable cardioverter-defibrillators (ICD) on the reduction of sudden cardiac death. Basing on the results of multiple clinical trials, left ventricular systolic function, measured as ejection fraction, is currently the only recommended tool to identify patients at higher risk of sudden death that would benefit from a prophylactic ICD. However, the systematic implementation of prophylactic ICD recommendations results in a substantial number of inappropriate ICD implantations, while failing to prevent the majority of sudden deaths occurring in the general population. That has been the case implementing arrhythmic risk stratification with a rough arrhythmic risk marker, such as ejection fraction, that lacks sensitivity and specificity in the prediction of sudden cardiac death. The aim of this viewpoint is to critically revise the value of ejection fraction in the identification of patients at risk of sudden cardiac death.

Contrast transoesophageal echocardiography remains superior to contrast-enhanced cardiac magnetic resonance imaging for the diagnosis of patent foramen ovale.

AIMS: In 30-40% of patients with acute ischaemic stroke, the cause remains undefined (cryptogenic stroke). Contrast transoesophageal echocardiography (TEE) is considered the gold standard for patent foramen ovale (PFO) detection. Recently, however, cardiac magnetic resonance (CMR) has also been applied to detect PFO. In this study, we compared the diagnostic value of CMR and TEE in detecting PFO in a group of patients with apparently cryptogenic stroke. METHODS AND RESULTS: Twenty-five patients (age 50 ± 13 years, 16 males) with apparently cryptogenic ischaemic stroke underwent contrast-enhanced TEE and contrast CMR for detection of possible PFO. Both imaging studies were performed during Valsalva manoeuvre. PFO grading results were assessed visually both for TEE and for CMR, according to the entity of contrast passage in the left atrium (grade 0 = no PFO; grades 1, 2, and 3 = mild, medium, and wide PFO, respectively). TEE detected PFO in 16 patients (64%). Contrast-enhanced CMR identified a PFO in 7 (44%) of these patients. TEE showed a grade 1 PFO in five patients, a grade 2 PFO in eight patients, and a grade 3 PFO in three patients. Of these patients, CMR failed to identify PFO in all five patients with a grade 1 PFO, in one patient with a grade 2 PFO, and one patient with grade 3 PFO according to TEE. None of the nine patients without PFO at TEE was shown to have a PFO at CMR. When compared with TEE, the present methodology of CMR had a sensitivity of 50%, specificity of 100%, negative predictive value of 31%, and a positive predictive value of 100%. CONCLUSION: Our data suggest that TEE is the cornerstone imaging diagnostic test to detect and characterize PFO in patients with ischaemic stroke, and is shown to be better compared with the current CMR sequences.

Intracardiac echocardiography in electrophysiology.

Intracardiac echocardiography (ICE) is a recent, invaluable tool which can provide real-time anatomical guidance in electrophysiological procedures. By inserting intravenously an ultrasound probe and advancing it into the heart, various different views can be obtained which allow to better visualize patient anatomy, to guide the placement of electrophysiological catheters, and to detect immediately procedural complications as they occur. In atrial fibrillation ablation, ICE proves particularly useful to achieve a safer trans-septal puncture (especially in the presence of anatomical anomalies of the interatrial septum) and to help to monitor the visualization of the mapping catheters (circular, high density), or the monitoring of the balloons catheter (Cryo, Laser) position. In ventricular tachycardia ablation, on the other hand, ICE allows for continuous correlation between electrophysiological and structural findings (such as wall motion anomalies or changes in echodensity), and helps to ensure correct catheter contact and to position it, particularly around delicate structures such as the aortic cusps. In any procedure, ICE is also useful to immediately detect procedural complications, such as thrombus formation along catheters, or pericardial effusion. Thanks to its real-time morphological information, ICE provides an ideal complement to simple fluoroscopy or to more complex electroanatomic mapping techniques and is set to gain a wider role in a broad range of electrophysiological procedures.

Association between reduced pulmonary diffusing capacity and cardiac autonomic dysfunction in Type 1 diabetes.

BACKGROUND: In Type 1 diabetes mellitus (DM), it has been suggested that autonomic nervous system dysfunction (NAD) impairs lung diffusion capacity. Heart rate variability (HRV), a measure of cardiac autonomic function, is a sensitive method of detecting NAD. To our knowledge, no previous study has assessed whether cardiac sympatho-vagal balance is associated with lung diffusion capacity in diabetes. METHODS: Twenty Type 1 DM patients without pulmonary abnormalities and systemic NAD underwent measurement of lung diffusion capacity for carbon monoxide (DLCO) by single-breath method and assessment of cardiac autonomic function by HRV analysis on 24-h electrocardiographic Holter recordings. RESULTS: Standard respiratory function tests and peripheral autonomic tests were normal in all patients. DLCO was lower than normal reference values in six patients (30%). DLCO correlated significantly with most HRV variables, independent of the clinical and laboratory variables. The strongest correlation was found with standard deviation of all RR intervals (SDNN; r = 0.62, P = 0.003) in the time domain and low frequency (LF) power (r = 0.73, P < 0.001) in the frequency domain. CONCLUSIONS: In Type 1 diabetes, a significant association exists between cardiac NAD and reduced DLCO in the absence of clinical respiratory and autonomic abnormalities. Thus, NAD may be involved in the early reduction of DLCO in these patients, possibly through abnormalities in the regulation of pulmonary blood flow at the microvascular level.

Effect of primary coronary intervention on heart rate variability and left ventricular function in patients with acute myocardial infarction.

AIM: Several studies showed that primary percutaneous coronary interventions (PCI) have a favourable impact on left ventricular remodeling and heart rate variability (HRV) both at short- and long-term follow-up in patients suffering an acute myocardial infarction (AMI). However, no previous study investigated the relationship between left ventricular remodeling and changes in HRV during follow-up in AMI patients treated by primary PCI. METHODS: We studied 28 patients with AMI (57+/-8 years, 27 men), treated by PCI within 12 hours of symptom onset. Patients underwent a 24-hour ECG Holter recording and left ventricular ejection fraction (LVEF) echocardiographic assessment before discharge, and at 1-month and 6-month follow-up. HRV was measured in the time- and frequency-domain. RESULTS: A significant improvement of both time- and frequency-domain HRV variables was observed at 1-month and at 6-month follow-up with the most significant changes being found for standard deviation of normal-normal beat intervals (SDNN) in the time-domain (95.5+/-26.1 ms vs 125.5+/-29.8 ms vs 142.8+/-28.8 ms, respectively; P<0.001) and for very low frequency (VLF) amplitude in the frequency-domain (36.7+/-9.8 ms vs 44.1+/-11.1 vs 48.9+/-12.2 ms, respectively; P<0.001). In contrast, compared to basal values, LVEF was substantially unchanged at 1-month and 6-month follow-up (48.8+/-8.5% vs 50.8+/-10% vs 49.6+/-9%, respectively; P=0.25). At 6-month follow-up 11 patients showed an improvement of >or= 5% of LVEF, whereas 17 patients did not show any improvement of LVEF. HRV variables significantly improved in a similar way in these two subgroups both at 1-month and at 6-month follow-up. CONCLUSION: Our data demonstrate that, in AMI patients treated by primary PCI, HRV improves over time, independent of changes in LVEF. The clinical implications of these findings deserve to be addressed in future studies.