Impact of 4D-Flow CMR Parameters on Functional Evaluation of Fontan Circulation.

We sought to evaluate the potential clinical role of 4D-flow cardiac magnetic resonance (CMR)-derived energetics and flow parameters in a cohort of patients' post-Fontan palliation. In patients with Fontan circulation who underwent 4D-Flow CMR, streamlines distribution was evaluated, as well a 4D-flow CMR-derived energetics parameters as kinetic energy (KE) and energy loss (EL) normalized by volume. EL/KE index as a marker of flow efficiency was also calculated. Cardiopulmonary exercise test (CPET) was also performed in a subgroup of patients. The population study included 55 patients (mean age 22 ± 11 years). The analysis of the streamlines revealed a preferential distribution of the right superior vena cava flow for the right pulmonary artery (62.5 ± 35.4%) and a mild preferential flow for the left pulmonary artery (52.3 ± 40.6%) of the inferior vena cave-pulmonary arteries (IVC-PA) conduit. Patients with heart failure (HF) presented lower IVC/PA-conduit flow (0.75 ± 0.5 vs 1.3 ± 0.5 l/min/m2, p = 0.004) and a higher mean flow-jet angle of the IVC-PA conduit (39.2 ± 22.8 vs 15.2 ± 8.9, p < 0.001) than the remaining patients. EL/KE index correlates inversely with VO2/kg/min: R: - 0.45, p = 0.01 peak, minute ventilation (VE) R: - 0.466, p < 0.01, maximal voluntary ventilation: R:0.44, p = 0.001 and positively with the physiological dead space to the tidal volume ratio (VD/VT) peak: R: 0.58, p < 0.01. From our data, lower blood flow in IVC/PA conduit and eccentric flow was associated with HF whereas higher EL/KE index was associated with reduced functional capacity and impaired lung function. Larger studies are needed to confirm our results and to further improve the prognostic role of the 4D-Flow CMR in this challenging population.

Overcoming Underpowering in the Outcome Analysis of Repaired-Tetralogy of Fallot: A Multicenter Database from the CMR/CT Working Group of the Italian Pediatric Cardiology Society (SICPed).

Background: Managing repaired tetralogy of Fallot (TOF) patients is still challenging despite the fact that published studies identified prognostic clinical or imaging data with rather good negative predictive accuracy but weak positive predictive accuracy. Heterogeneity of the initial anatomy, the surgical approach, and the complexity of the mechanism leading to dilation and ventricular dysfunction explain the challenge of predicting the adverse event in this population. Therefore, risk stratification and management of this population remain poorly standardized. Design: The CMR/CT WG of the Italian Pediatric Cardiology Society set up a multicenter observational clinical database of repaired TOF evaluations. This registry will enroll patients retrospectively and prospectively assessed by CMR for clinical indication in many congenital heart diseases (CHD) Italian centers. Data collection in a dedicated platform will include surgical history, clinical data, imaging data, and adverse cardiac events at 6 years of follow-up. Summary: The multicenter repaired TOF clinical database will collect data on patients evaluated by CMR in many CHD centers in Italy. The registry has been set up to allow future research studies in this population to improve clinical/surgical management and risk stratification of this population.

Dobutamine Stress Cardiac MRI in Pediatric Patients with Suspected Coronary Artery Disease.

Following current practice, pediatric patients with treated congenital coronary malformations or acquired coronary disease undergo Cardio-Pulmonary Exercise Test (CPET), stress Echocardiography and Electrocardiography (sEcho, sEKG), and Coronary Angiography (CA). Stress cMRI can assess cardiac function, myocardial viability, and stress/rest perfusion deficit-without radiation exposure, general anesthesia, and hospitalization-in a single non-invasive exam. The aim of our pilot study is to assess the feasibility and diagnostic accuracy of Dobutamine stress cMRI compared to the current procedures (sEcho, CPET, CA). The prospective study is focused on pediatric patients, at risk for or with previously diagnosed coronary artery disease: d-looped TGA after arterial Switch, Kawasaki disease, and anomalous origin of left coronary artery from pulmonary artery (ALCAPA) after coronary artery reimplantation. We have compared the results of MRI coronary angiography, and Dobutamine stress cMRI with traditional tests. All these diagnostic exams were acquired in a timeframe of 3 month, in a blinded fashion. All the 13 patients (age: 12 ± 2 years, median 12,7 y) recruited, completed the study without major adverse events. The mean heart rate-pressure product was 25,120 ± 5110 bpm x mm Hg. The target heart rate of 85% of the maximal theoretical was reached by 10 (77%) patients. The comparison between cardiac MRI coronarography versus the gold standard Coronary Angiography to identify the patency of the origin and the proximal pathway of the coronary arteries shows a sensitivity of 100% (confidence interval: 2,5-100%), specificity 92% (confidence interval: 64-100%). The stress test was well tolerated for the 77% of the patients and completed by the totality of patients (Table 3). Three patients (23%) had mild symptoms: nausea, vomiting, or general discomfort. In pediatric patients with a potential or definite diagnosis of coronary artery disease, stress cMRI combines an effective assessment of proximal coronary arteries anatomy with cardiac function, myocardial perfusion, and viability in a single examination. Stress cMRI can be proposed as alternative, standalone test.

Long-Term Cardiovascular Outcome in Children with MIS-C Linked to SARS-CoV-2 Infection-An Italian Multicenter Experience.

MIS-C is a multisystem inflammatory syndrome that is characterized by multi-organ failure and cardiac involvement. The aim of this study was to describe the long-term cardiovascular outcome in a cohort of MIS-C pediatric patients, who were admitted to two Italian Pediatric Referral Centers. Sixty-seven patients (mean age 8.7 ± 4.7 years, male 60%) were included; 65 (97%) of them showed cardiac involvement. All of the patients completed one month of the follow-up, and 47% completed 1 year of it. ECG abnormalities were present in 65% of them, arrhythmias were present in 9% of them during an acute phase and it disappeared at the point of discharge or later. Pericarditis were detected in 66% of them and disappeared after 6 months. Coronaritis was observed in 35% of the children during an acute phase, and there were no more instances at the 1-year point. An LV dysfunction was present in 65% of the patients at the beginning of the study, with them having a full recovery at the point of discharge and thereafter. Elevated values of the NTproBNP and hsTp were initially detected, which progressively decreased and normalized at the points of discharge and FU. The CMR at the point of FU, there was a presence of long-term myocardial scars in 50% of the patients that were tested. No deaths that were caused by MIS-C during the FU were recorded. Cardiac involvement in MIS-C patients is almost the rule, but the patients' clinical course was satisfactory, and no additional events or sequelae were observed apart from there being long-term myocardial scars in 50% of the patients that underwent CMR.

Long term follow-up in two siblings with Sengers syndrome: Case report.

BACKGROUND: Sengers syndrome is characterized by congenital cataract, hypertrophic cardiomyopathy, mitochondrial myopathy, and lactic acidosis associated with mutations in AGK gene. Clinical course ranges from a severe fatal neonatal form, to a more benign form allowing survival into adulthood, to an isolated form of congenital cataract. Thus far few reported cases have survived the second decade at their latest examination, and no natural history data are available for the disease. CASE PRESENTATION: Here we provide a 20-year follow-up in two siblings with a benign form of Sengers syndrome, expanding the phenotypical spectrum of the disease by reporting a condition of ovarian agenesis. CONCLUSION: To our knowledge, this report provides the first longitudinal data of Sengers syndrome patients.

Recommendations for cardiovascular magnetic resonance and computed tomography in congenital heart disease: a consensus paper from the CMR/CCT working group of the Italian Society of Pediatric Cardiology (SICP) and the Italian College of Cardiac Radiology endorsed by the Italian Society of Medical and Interventional Radiology (SIRM) Part I.

Cardiovascular magnetic resonance (CMR) and computed tomography (CCT) are advanced imaging modalities that recently revolutionized the conventional diagnostic approach to congenital heart diseases (CHD), supporting echocardiography and often replacing cardiac catheterization. Nevertheless, correct execution and interpretation require in-depth knowledge of all technical and clinical aspects of CHD, a careful assessment of risks and benefits before each exam, proper imaging protocols to maximize diagnostic information, minimizing harm. This position paper, written by experts from the Working Group of the Italian Society of Pediatric Cardiology and from the Italian College of Cardiac Radiology of the Italian Society of Medical and Interventional Radiology, is intended as a practical guide for applying CCT and CMR in children and adults with CHD, wishing to support Radiologists, Pediatricians, Cardiologists and Cardiac Surgeons in the multimodality diagnostic approach to these patients. The first part provides a review of the most relevant literature in the field, describes each modality's advantage and drawback, making considerations on the main applications, image quality, and safety issues. The second part focuses on clinical indications and appropriateness criteria for CMR and CCT, considering the level of CHD complexity, the clinical and logistic setting and the operator expertise.

Cardiovascular Manifestations in Multisystem Inflammatory Syndrome in Children (MIS-C) Associated with COVID-19 According to Age.

Cardiac involvement in multisystem inflammatory syndrome in children (MIS-C) associated with coronavirus-19 disease is often observed with a high risk of heart failure. The aim is to describe cardiovascular involvement, management and early outcome in MIS-C by comparing cardiovascular manifestations in children younger and older than 6 years old. This retrospective observational study included 25 children with MIS-C, admitted to a single pediatric center between March 2020 and September 2021. The median age was 5 years (13 patients under 6 years and 12 over 6 years); coronary artery abnormalities were observed in 77% of preschoolers, with small and medium aneurysms in half of the cases and two cases of mild ventricular dysfunction. School-age children presented myopericardial involvement with mild to moderate ventricular dysfunction in 67% of cases, and two cases of transient coronary dilatation. There was a significant NT-pro-BNP and inflammatory markers increase in 25 of the patients, and mild elevation of troponin I in 9. All patients were treated with intravenous immunoglobulin and corticosteroids, and 8 with anakinra. None of the patients needed inotropes or intensive care unit admission. Our study shows the frequent cardiovascular involvement in MIS-C with a peculiar distribution, according to different age group: coronary artery anomalies were more frequent in the younger group, and myopericardial disease in the older one. A prompt multitarget, anti-inflammatory therapy could probably contribute to a favorable outcome.

[An up-to-date telemedicine integrated clinical pathway for adult patients with congenital heart disease]. / Un nuovo percorso di cura integrato con la telemedicina per la gestione del paziente adulto con cardiopatia congenita.

Clinical management of adult patients with congenital heart disease (GUCH) is a difficult task for multiple reasons, which include their own pathology and clinical history complexity, diagnostic complexity and organization of care. GUCH specialists are present in very small numbers and are concentrated in few centers, thus generating considerable transfer problems for patients. During the COVID-19 pandemic, telemedicine has become the standard of care, ensuring health assistance continuity, and implementing communication channels between patients and health professionals. We suggest to stratify GUCH patients into three groups, which correspond to different levels of risk (low, moderate and high, respectively) to develop complications over time, using a GUCH-specific multiparametric complexity score; so, each patient pathway will be defined according to the specific group, with indication of site, timing and type of clinical and instrumental evaluations, including virtual visits and consults. In conclusion, practical tools are provided for the implementation of updated care pathways for GUCH patients, who finally are inserted in a new model of care in which even if in-person visit still represents the crucial moment of each patient care pathway, on the other hand, telemedicine incorporation could contribute to improving and making even more complete and effective GUCH patient care.

Cardiac Manifestations in Children with SARS-COV-2 Infection: 1-Year Pediatric Multicenter Experience.

Since the spread of COVID-19, pediatric patients were initially considered less affected by SARS-COV-2, but current literature reported subsets of children with multisystem inflammatory syndrome (MIS-C). This study aims to describe the cardiac manifestation of SARS-COV-2 infection in a large cohort of children admitted to two Italian pediatric referral centers. Between March 2020 and March 2021, we performed a cardiac evaluation in 294 children (mean age 9 ± 5.9 years, male 60%) with active or previous SARS-COV-2 infection. Twenty-six showed ECG abnormalities: 63 repolarization anomalies, 13 Long QTc, five premature ventricular beats, two non-sustained ventricular tachycardia, and one atrial fibrillation. In total, 146 patients underwent cardiac biomarkers: NT-proBNP was elevated in 57, troponin in 34. An echocardiogram was performed in 98, showing 54 cardiac anomalies: 27 left-ventricular dysfunction, 42 pericarditis, 16 coronaritis. MIS-C was documented in 46 patients (mean age 9 ± 4.8 years, male 61%) with cardiac manifestations in 97.8%: 27 ventricular dysfunctions, 32 pericarditis, 15 coronaritis, 3 arrhythmias. All patients recovered, and during follow-up, no cardiac anomalies were recorded. Our experience showed that cardiac involvement is not rare in children with SARS-COV-2, and occurred in almost all patients with MIS-C. However, patients' recovery is satisfactory and no additional events were reported during FU.

[Physical activity in patients with repaired and unrepaired congenital heart diseases. Task Force for exercise prescription in patients with congenital heart disease of the Italian Society of Pediatric Cardiology and Congenital Heart Disease]. / L'attività fisica nei soggetti con cardiopatia congenita in storia naturale ed operata. Task Force sull'attività fisica nel cardiopatico congenito della Società Italiana di Cardiologia Pediatrica e delle Cardiopatie Congenite.

Regular physical activity is essential for physical health and mental wellbeing in children and teenagers. However, patients with congenital heart disease are often restricted from being physically active due to parental overprotection and lack of physical activity promotion or exercise prescription from their physicians. A comprehensive medical evaluation is crucial for the development of personalized exercise programs for these patients. The aim of this review is to provide physicians with a practical guide on how to promote physical activity and prescribe exercise for patients with congenital heart disease with or without surgical correction.

Cardiovascular MRI assessment of pectus excavatum in pediatric patients and postoperative simulation using vacuum bell.

BACKGROUND: The sternal lift by Vacuum Bell (VB) is effective, as largely demonstrated by its intraoperative use during surgical procedure to elevate the sternum during the Nuss procedure routinely. Indeed, the thoracic remodelling during VB application is comparable to post-surgical scenario, and suitable to compare cardiovascular parameters of the two different thoracic configurations immediately. OBJECTIVE: We would quantify and correlate preoperative parameters which determine the severity of the pectus excavatum (PE), and the cardiovascular effects at the baseline. Than we would assess the cardiovascular changes during VB positioning, mimicking the immediate, temporary effect of Pectus-correction. MATERIALS AND METHODS: We included 26 consecutive patients (mean age is 13,3 +/- 2,2 years) symptomatic and non, with a previous clinical diagnosis of PE. CMR was performed before and during application of VB, using the same imaging protocol. In both conditions, we measured thoracic indexes, and cardiac function as well as flow through main vessels. RESULTS: Mean expiratory Haller Index (HI) was 5,4 (+/-1,4 SD; normal <3). During VB application, all patients showed improvement in the main morphologic parameters of the thorax (mean expiratory HI = 4,7 (+/-1,6 SD, delta -13%, P = 0,01). During VB application, a minimal but not significant increase of Right Ventricle End Diastolic Volume (RVEDVi) (delta +4,6%, P = 0,12), and Right Ventricle Ejection Fraction (RVEF) (delta +1,2%, P = 0,2) was observed. CONCLUSION: In adolescents affected by PE, cardiacMRI (CMR) demonstrates normal values of biventricular volume and systolic function. During VB application, beside significative improvements in chest wall anatomy, CMR shows a minimal positive variation in right ventricle volume and function. A minority of patients showed some degree of diastolic dysfunction at baseline, unchanged after VB application, with possible correlation between valve inflow and sternal impingement.

Left ventricular dysfunction in repaired tetralogy of Fallot: incidence and impact on atrial arrhythmias at long term-follow up.

Left ventricle (LV) systolic dysfunction in repaired tetralogy of Fallot (TOF) has been identified as a risk factor for functional status and adverse outcome. The aims of this cross-sectional followed by a prospective study were: (1) to evaluate the prevalence of LV systolic dysfunction in a large cohort of adults with repaired tetralogy of Fallot, (2) to test the relationship between LV systolic dysfunction and other known risk factors and (3) to evaluate the impact of LV systolic dysfunction on adverse cardiac events. In a multicenter study, 237 adults repaired TOF (58 % males, age 30 ± 10 years) were evaluated by cardiac magnetic resonance (CMR). Demographics, surgical history, ECG, Echo-Color Doppler and follow-up data were recorded. LV was dilated (Z value >2) in 16 patients (6 %), however 56 patients (23.6 %) had a reduced LV systolic function left ventricle ejection fraction (LVEF) (Z value <-2). Patients with LV systolic dysfunction were mainly males (82 %), had reduced right ventricle ejection fraction (RVEF), and higher right and left Late Gadolinium Enhanced scores. In a multivariate regression analysis male gender and RVEF resulted to be independent factors associated to LV systolic dysfunction. Atrial arrhythmias were the main adverse cardiac event at the follow-up and were associated to higher biventricular volumes and lower biventricular ejection fraction (EF); however multivariable analysis identified age, right ventricle end-diastolic volume (RVEDVi) and tricuspid regurgitation as independents factors associated to atrial arrhythmias. At long term follow-up at least » of repaired TOF has LV dysfunction. Lower LVEF is associated to male gender and lower RVEF.

Identification of TBX5 mutations in a series of 94 patients with Tetralogy of Fallot.

Tetralogy of Fallot (TOF) (OMIM #187500) is the most frequent conotruncal congenital heart defect (CHD) with a range of intra- and extracardiac phenotypes. TBX5 is a transcription factor with well-defined roles in heart and forelimb development, and mutations in TBX5 are associated with Holt-Oram syndrome (HOS) (OMIM#142900). Here we report on the screening of 94 TOF patients for mutations in TBX5, NKX2.5 and GATA4 genes. We identified two heterozygous mutations in TBX5. One mutation was detected in a Moroccan patient with TOF, a large ostium secundum atrial septal defect and complete atrioventricular block, and features of HOS including bilateral triphalangeal thumbs and fifth finger clinodactyly. This patient carried a previously described de novo, stop codon mutation (p.R279X) located in exon 8 causing a premature truncated protein. In a second patient from Italy with TOF, ostium secundum atrial septal defect and progressive arrhythmic changes on ECG, we identified a maternally inherited novel mutation in exon 9, which caused a substitution of a serine with a leucine at amino acid position 372 (p.S372L, c.1115C>T). The mother's clinical evaluation demonstrated frequent ventricular extrasystoles and an atrial septal aneurysm. Physical examination and radiographs of the hands showed no apparent skeletal defects in either child or mother. Molecular evaluation of the p.S372L mutation demonstrated a gain-of-function phenotype. We also review the literature on the co-occurrence of TOF and HOS, highlighting its relevance. This is the first systematic screening for TBX5 mutations in TOF patients which detected mutations in two of 94 (2.1%) patients.

Tricuspid annular plane systolic excursion for the assessment of ventricular function in adults operated on with mustard procedure for complete transposition of the great arteries.

BACKGROUND: In adult patients with d-transposition of the great arteries after atrial switch operation, dysfunction of the systemic right ventricle (RV) is a well-known complication. Echocardiographic variables may provide adequate estimation of subpulmonary RV function, but their applicability to the subaortic RV is not straightforward. We evaluate the concordance between tricuspid annular plane systolic excursion (TAPSE) and magnetic resonance imaging-derived ejection fraction of the RV (MRI-RVEF) in these patients. METHODS: Patients were recruited from those evaluated at the adult congenital clinic of our department between 2010 and 2012. All patients who had an echocardiographic assessment within 6 months of their MRI examination were selected. Patients clinically unstable, not in sinus rhythm, with a prosthetic systemic atrioventricular valve, permanent pacemaker, or more than moderate systemic atrioventricular valve regurgitation were excluded. RESULTS: Eighteen Mustard-operated patients aged 22 ± 3.7 years were studied. The mean values of TAPSE and RVEF were 13.22 ± 1.7 mm and 49.7 ± 6%, respectively. TAPSE and RVEF were normal in 1 (5.5%) and 10 (55.5%) patients, respectively. Seventeen (94.4%) patients showed reduced TAPSE (12.9 ± 1.3 mm): RVEF was reduced in eight (47%) of these subjects, and normal in nine (53%). In patients with normal RVEF, both the MRI-RV end-diastolic and the MRI-RV end-systolic volumes were significantly lower than in patients with reduced RVEF. There were no other statistically significant differences between these patients. No correlation was found between TAPSE and both the MRI-RV end-diastolic and the end-systolic volumes. Globally, agreement between TAPSE and RVEF was slight (K = 0.09 ± 0.089). CONCLUSIONS: Our results indicate that in these patients TAPSE is not a useful measure of RV function.

Subclinical cardiac dysfunction and exercise performance in childhood cancer survivors.

BACKGROUND: Although anthracycline cardiotoxicity is clearly related to the cumulative dose administered, subclinical cardiac dysfunction has been reported across a wide range of treatment regimens, and its clinical significance is still unclear. Purpose of this study is to investigate by exercise echocardiography for subclinical cardiac dysfunction in survivors of pediatric cancer treated with low-moderate anthracycline doses, and to evaluate whether it may alter the response of the cardiovascular system to dynamic exercise. PROCEDURE: Post-exercise left ventricular end-systolic wall stress (ESS), left ventricular posterior wall dimension and percent thickening at end systole, and cardiopulmonary exercise test-derived indexes of cardiac function were examined in 55 apparently healthy patients (mean age 13.5 ± 2.9 years, median anthracycline cumulative dose 240 mg/m(2)) and in 63 controls. RESULTS: Subclinical cardiac dysfunction was identified in 17 patients (30%) presenting reduced left ventricular posterior wall dimension or percent thickening, or increased values of left ventricular ESS as compared to controls (group A), while the remaining patients formed group B. Reduced oxygen consumption at peak exercise in both groups of patients was the only cardiopulmonary exercise test variable resulting significantly different between patients and controls: no differences were found among the groups of patients. CONCLUSIONS: Our results confirm that even patients treated with a median anthracycline dose of 240 mg/m(2) (range 100-490) are at considerable risk of exhibiting subclinical cardiac dysfunction that, however, does not seem to alter the physiologic response of the cardiovascular system to dynamic exercise.

Stenting of aortic coarctation and exercise-induced hypertension in the young.

OBJECTIVES: To evaluate whether the stenting of aortic coarctation enhance the risk of exercise-induced hypertension (EIH). BACKGROUND: There is the theoretical concern that aortic stents may cause increased aortic wall impedance and therefore systolic hypertension during exercise. METHODS: Blood pressure and the Doppler derived peak and mean systolic pressure gradient (PSG and MSG) across the distal aorta at the peak of exercise were evaluated in young patients (mean age 14 +/- 3 years) with aortic coarctation successfully treated with surgery or with stent implantation at least 1 year before the test. Only patients who reached the 85% maximal predicted heart rate or whose exercise test was interrupted because of severe hypertension, and in whom significant aortic narrowings were excluded by a MRI or a CT scan performed in the six months preceding the exercise test were included in the study. RESULTS: Seventeen patients formed the surgery-group, while 15 patients the stent-group. Patients in surgery-group were younger at coarctation repair and with a longer follow-up than those in stent-group. No difference was present regarding age, body surface area, gender, and presence, and degree of mildly hypoplastic aortic segments between the two groups as well as between patients with or without EIH. EIH was found in 35% of surgery-group patients and in 33% of stent-group patients. PSG and MSG were similar in the patients with or without EIH. CONCLUSIONS: EIH can be found in a high number of young patients successfully treated for aortic coarctation but at intermediate follow-up stent implantation does not seem to enhance the risk of EIH.

Aortic arch geometry and exercise-induced hypertension in aortic coarctation.

Hypertension at rest or during effort is not uncommon in patients with aortic coarctation (CoA), even those with a successful repair or mild degree of obstruction. Anatomic factors and functional abnormalities have been proposed as causes of this finding. Recently, aortic arch geometry was reported in association with hypertension at rest in patients with successful CoA repair. Forty-one patients (age 15.7 +/- 4.6 years) without significant obstruction at rest (mean systolic Doppler gradient at rest < or =25 mm Hg) were selected for the study. All patients underwent a maximal cardiopulmonary exercise test and magnetic resonance imaging of the aorta. Aortic arch shape was defined on global geometry as normal, gothic, and crenel. Percentage of anatomic narrowing (AN) was also calculated. Twenty-four patients (58%) showed exercise-induced hypertension (EIH). Regarding the shape of the aortic arch, normal geometry was present in 17 patients (41%), 9 (21%) had gothic geometry, and 15 (36%) had crenel geometry. There were no differences among the 3 geometries in regard to the incidence of EIH (70.6% in normal, 55.6% in gothic, and 46.7% in crenel) or AN (36.9% in normal, 33.5% in gothic, and 36.6% in crenel). In conclusion, our results fail to show a correlation between a specific aortic arch shape and the incidence of EIH and significant AN in patients with native or residual CoA or repeat CoA. Therefore, at present, the role of aortic arch geometry in identifying patients at risk of EIH is still uncertain.

Attenuation of induced bronchoconstriction in healthy subjects: effects of breathing depth.

The effects of breathing depth in attenuating induced bronchoconstriction were studied in 12 healthy subjects. On four separate, randomized occasions, the depth of a series of five breaths taken soon (approximately 1 min) after methacholine (MCh) inhalation was varied from spontaneous tidal volume to lung volumes terminating at approximately 80, approximately 90, and 100% of total lung capacity (TLC). Partial forced expiratory flow at 40% of control forced vital capacity (V(part)) and residual volume (RV) were measured at control and again at 2, 7, and 11 min after MCh. The decrease in V(part) and the increase in RV were significantly less when the depth of the five-breath series was progressively increased (P < 0.001), with a linear relationship. The attenuating effects of deep breaths of any amplitude were significantly greater on RV than V(part) (P < 0.01) and lasted as long as 11 min, despite a slight decrease with time when the end-inspiratory lung volume was 100% of TLC. In conclusion, in healthy subjects exposed to MCh, a series of breaths of different depth up to TLC caused a progressive and sustained attenuation of bronchoconstriction. The effects of the depth of the five-breath series were more evident on the RV than on V(part), likely due to the different mechanisms that regulate airway closure and expiratory flow limitation.