[Optimizing the care management pathway of patients with ischemia and non-obstructive coronary arteries]. / Ottimizzazione del percorso clinico-gestionale del paziente con ischemia in assenza di malattia coronarica ostruttiva.

Ischemia with non-obstructive coronary arteries (INOCA) is defined by the coexistence of anginal symptoms and demonstrable ischemia, with no evidence of obstructive coronary arteries. The underlying mechanism of INOCA is coronary microvascular dysfunction with or without associated vasospasm. INOCA patients have recurrent symptoms, functional limitations, repeated access to the emergency department, impaired quality of life and a higher incidence of cardiovascular events than the general population. Although well described in chronic coronary syndrome guidelines, INOCA remains underdiagnosed in clinical practice because of insufficient awareness, lack of accurate diagnostic tools, and poorly standardized and consistent definitions to diagnose, both invasively and non-invasively, coronary microvascular dysfunction.To disseminate current scientific evidence on INOCA as a distinct clinical entity, during 2022 we conducted at 30 cardiology units all over the country a clinical practice improvement initiative, with the aim of developing uniform and shared management pathways for INOCA patients across different operational settings. The present document highlights the outcomes of this multidisciplinary initiative.

Identification of determinants of lipid and ion transport in TMEM16/anoctamin proteins through a Bayesian statistical analysis.

The TMEM16/Anoctamin protein family (TMEM16x) is composed of members with different functions; some members form Ca2+-activated chloride channels, while others are lipid scramblases or combine the two functions. TMEM16x proteins are typically activated in response to agonist-induced rises of intracellular Ca2+; thus, they couple Ca2+-signalling with cell electrical activity or plasmalemmal lipid homeostasis. The structural domains underlying these functions are not fully defined. We used a Naïve Bayes classifier to gain insights into these domains. The method enabled identification of regions involved in either ion or lipid transport, and suggested domains for possible pharmacological exploitation. The method allowed the prediction of the transport property of any given TMEM16x. We envisage this strategy could be exploited to illuminate the structure-function relationship of any protein family composed of members playing different molecular roles.

The TMEM16A channel as a potential therapeutic target in vascular disease.

PURPOSE OF REVIEW: The transmembrane protein 16A (TMEM16A) Ca 2+ -activated Cl - channel constitutes a key depolarising mechanism in vascular smooth muscle and contractile pericytes, while in endothelial cells the channel is implicated in angiogenesis and in the response to vasoactive stimuli. Here, we offer a critical analysis of recent physiological investigations and consider the potential for targeting TMEM16A channels in vascular disease. RECENT FINDINGS: Genetic deletion or pharmacological inhibition of TMEM16A channels in vascular smooth muscle decreases artery tone and lowers systemic blood pressure in rodent models. Inhibition of TMEM16A channels in cerebral cortical pericytes protects against ischemia-induced tissue damage and improves microvascular blood flow in rodent stroke models. In endothelial cells, the TMEM16A channel plays varied roles including modulation of cell division and control of vessel tone through spread of hyperpolarisation to the smooth muscle cells. Genetic studies implicate TMEM16A channels in human disease including systemic and pulmonary hypertension, stroke and Moyamoya disease. SUMMARY: The TMEM16A channel regulates vascular function by controlling artery tone and capillary diameter as well as vessel formation and histology. Preclinical and clinical investigations are highlighting the potential for therapeutic exploitation of the channel in a range of maladaptive states of the (micro)circulation.

The TMEM16A anion channel as a versatile regulator of vascular tone.

The TMEM16A channel represents a key depolarizing mechanism in arterial smooth muscle and contractile pericytes, where it is activated by several endogenous contractile agonists. In this issue of Science Signaling, Mata-Daboin et al. demonstrate a previously unidentified role for TMEM16A in endothelial cells for acetylcholine-mediated vasorelaxation. Collectively, TMEM16A serves as a transducer of vasoactive stimuli to enable fine modulation of vessel tone.

Long-term dual antiplatelet therapy and nuisance bleeding: impact on quality of life.

Long term dual antiplatelet therapy (LTDAPT), with ticagrelor 60 mg and low-dose aspirin, is indicated after acute coronary syndrome (ACS) for the secondary prevention of atherothrombotic events in high-risk patients with a history of ACS of at least 1 year. LTDAPT had a good tolerability and safety profile, but the risk of TIMI major bleeding was increased. However, even non-significant bleeding may be important because it has an effect on the quality of life and therefore may lead to treatment discontinuation. We, therefore, evaluated patients' experiences with LTDAPT and the impact of nuisance bleeding on quality of life and treatment adherence. We retrospectively reviewed 225 patients in follow-up after ACS with at least one high-risk condition, treated with ticagrelor 60 mg twice daily (after 90 mg twice daily for 12 months). The outpatient follow-up program after hospitalization provides a visit on day 30 after discharge, then after 3 months, continuing with six-monthly checks. We assessed the presence and intensity of bleeding, as well as health-related quality of life (HRQoL), at each visit. The TIMI score was used to determine the severity of the bleeding. Any overt bleeding event that did not meet the major and minor criteria was labeled "minimal" and could be framed as "nuisance bleeding." The HRQoL was assessed by the EuroQol-5 and Dimension (EQ-5D) visual analog scale (VAS) score. Minimal bleedings were present in 49 patients (21%), but only in one case (by decision of the patient) there was a cause for discontinuation of therapy. However, 39 (79%) subjects had asked for opinions on stopping the therapy during the telephone consultation. Factors influencing LTDAPT knowledge included access to medication counselling, engaging with information communicated during medication counselling, and access to timely, relevant and expert information and advice after discharge from the hospital. All adverse events, judged to be "not serious" in trials, may have an effect on the quality of life and therefore may lead to treatment discontinuation. The authors underline the importance of careful outpatient follow-up and ongoing counselling, to check out compliance and possible adverse effect of LTDAPT.

The pharmacology of the TMEM16A channel: therapeutic opportunities.

The TMEM16A Ca2+-gated Cl- channel is involved in a variety of vital physiological functions and may be targeted pharmacologically for therapeutic benefit in diseases such as hypertension, stroke, and cystic fibrosis (CF). The determination of the TMEM16A structure and high-throughput screening efforts, alongside ex vivo and in vivo animal studies and clinical investigations, are hastening our understanding of the physiology and pharmacology of this channel. Here, we offer a critical analysis of recent developments in TMEM16A pharmacology and reflect on the therapeutic opportunities provided by this target.

The Ca2+-gated channel TMEM16A amplifies capillary pericyte contraction and reduces cerebral blood flow after ischemia.

Pericyte-mediated capillary constriction decreases cerebral blood flow in stroke after an occluded artery is unblocked. The determinants of pericyte tone are poorly understood. We show that a small rise in cytoplasmic Ca2+ concentration ([Ca2+]i) in pericytes activated chloride efflux through the Ca2+-gated anion channel TMEM16A, thus depolarizing the cell and opening voltage-gated calcium channels. This mechanism strongly amplified the pericyte [Ca2+]i rise and capillary constriction evoked by contractile agonists and ischemia. In a rodent stroke model, TMEM16A inhibition slowed the ischemia-evoked pericyte [Ca2+]i rise, capillary constriction, and pericyte death; reduced neutrophil stalling; and improved cerebrovascular reperfusion. Genetic analysis implicated altered TMEM16A expression in poor patient recovery from ischemic stroke. Thus, pericyte TMEM16A is a crucial regulator of cerebral capillary function and a potential therapeutic target for stroke and possibly other disorders of impaired microvascular flow, such as Alzheimer's disease and vascular dementia.

Polymodal Control of TMEM16x Channels and Scramblases.

The TMEM16A/anoctamin-1 calcium-activated chloride channel (CaCC) contributes to a range of vital functions, such as the control of vascular tone and epithelial ion transport. The channel is a founding member of a family of 10 proteins (TMEM16x) with varied functions; some members (i.e., TMEM16A and TMEM16B) serve as CaCCs, while others are lipid scramblases, combine channel and scramblase function, or perform additional cellular roles. TMEM16x proteins are typically activated by agonist-induced Ca2+ release evoked by Gq-protein-coupled receptor (GqPCR) activation; thus, TMEM16x proteins link Ca2+-signalling with cell electrical activity and/or lipid transport. Recent studies demonstrate that a range of other cellular factors-including plasmalemmal lipids, pH, hypoxia, ATP and auxiliary proteins-also control the activity of the TMEM16A channel and its paralogues, suggesting that the TMEM16x proteins are effectively polymodal sensors of cellular homeostasis. Here, we review the molecular pathophysiology, structural biology, and mechanisms of regulation of TMEM16x proteins by multiple cellular factors.

Long term dual antiplatelet therapy after myocardial infarction: retrospective analysis in an outpatient population.

Long term treatment with ticagrelor 60 mg and low-dose aspirin are indicated after acute coronary syndrome (ACS). We retrospectively reviewed aggregate data of 187 patients (155 M and 38 F) (mean age 63.8±9 years) in follow up after ACS with at least one high risk condition (Multivessel disease, diabetes, GFR<60 mL/min, history of prior myocardial infarction, age >65 years) treated with ticagrelor 60 mg twice daily (after 90 mg twice daily for 12 months). The results were compared with findings (characteristics of the patients at baseline, outcomes, bleeding) of PEGASUS-TIMI 54 trial and Eu Label. The highrisk groups were represented as follows: multivessel disease 105 pts (82%), diabetes 63 pts (33%), GFR< 60 mL/min 27 pts (14%), history of prior MI 33 pts (17%), >65 year aged 85 pts (45%). Treatment was withdrawn in 7 patients: 3 cases showed atrial fibrillation and were placed on oral anticoagulant drugs, one developed intracranial bleeding, in three patients a temporary withdrawal was due to surgery (1 colon polyposis and 2 cases of bladder papilloma). Chest pain without myocardial infarction occurred in 16 patients (revascularization was required in 9 patients). Dyspnea was present in 15 patients, but was not a cause for discontinuation of therapy. Long term treatment with ticagrelor 60 mg twice daily plus aspirin 100 mg/day showed a favourable benefit/risk profile after ACS.  In this study all patients had been given ticagrelor 90 mg twice daily for 12 months and the 60 mg twice daily dosage was started immediately thereafter, unlike PEGASUS-TIMI 54 trial in which it was prescribed within a period ranging from 1 day to 1 year after discontinuation of the 90 mg dose. This makes our results more consistent with current clinical practice. However, a careful outpatient follow-up and constant counseling are mandatory to check out compliance to therapy and adverse side effects.

Ion channels as convergence points in the pathology of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a fatal disease of the cardiopulmonary system that lacks curative treatments. The main pathological event in PAH is elevated vascular resistance in the pulmonary circulation, caused by abnormal vasoconstriction and vascular remodelling. Ion channels are key determinants of vascular smooth muscle tone and homeostasis, and four PAH channelopathies (KCNK3, ABCC8, KCNA5, TRPC6) have been identified so far. However, the contribution of ion channels in other forms of PAH, which account for the majority of PAH patients, has been less well characterised. Here we reason that a variety of triggers of PAH (e.g. BMPR2 mutations, hypoxia, anorectic drugs) that impact channel function may contribute to the onset of the disease. We review the molecular mechanisms by which these 'extrinsic' factors converge on ion channels and provoke their dysregulation to promote the development of PAH. Ion channels of the pulmonary vasculature are therefore promising therapeutic targets because of the modulation they provide to both vasomotor tone and proliferation of arterial smooth muscle cells.

An outer-pore gate modulates the pharmacology of the TMEM16A channel.

TMEM16A Ca2+-activated chloride channels are involved in multiple cellular functions and are proposed targets for diseases such as hypertension, stroke, and cystic fibrosis. This therapeutic endeavor, however, suffers from paucity of selective and potent modulators. Here, exploiting a synthetic small molecule with a biphasic effect on the TMEM16A channel, anthracene-9-carboxylic acid (A9C), we shed light on sites of the channel amenable for pharmacological intervention. Mutant channels with the intracellular gate constitutively open were generated. These channels were entirely insensitive to extracellular A9C when intracellular Ca2+ was omitted. However, when physiological Ca2+ levels were reestablished, the mutants regained sensitivity to A9C. Thus, intracellular Ca2+ is mandatory for the channel response to an extracellular modulator. The underlying mechanism is a conformational change in the outer pore that enables A9C to enter the pore to reach its binding site. The explanation of this structural rearrangement highlights a critical site for pharmacological intervention and reveals an aspect of Ca2+ gating in the TMEM16A channel.

The structural basis of lipid scrambling and inactivation in the endoplasmic reticulum scramblase TMEM16K.

Membranes in cells have defined distributions of lipids in each leaflet, controlled by lipid scramblases and flip/floppases. However, for some intracellular membranes such as the endoplasmic reticulum (ER) the scramblases have not been identified. Members of the TMEM16 family have either lipid scramblase or chloride channel activity. Although TMEM16K is widely distributed and associated with the neurological disorder autosomal recessive spinocerebellar ataxia type 10 (SCAR10), its location in cells, function and structure are largely uncharacterised. Here we show that TMEM16K is an ER-resident lipid scramblase with a requirement for short chain lipids and calcium for robust activity. Crystal structures of TMEM16K show a scramblase fold, with an open lipid transporting groove. Additional cryo-EM structures reveal extensive conformational changes from the cytoplasmic to the ER side of the membrane, giving a state with a closed lipid permeation pathway. Molecular dynamics simulations showed that the open-groove conformation is necessary for scramblase activity.

Defining the ionic mechanisms of optogenetic control of vascular tone by channelrhodopsin-2.

BACKGROUND AND PURPOSE: Optogenetic control of electromechanical coupling in vascular smooth muscle cells (VSMCs) is emerging as a powerful research tool with potential applications in drug discovery and therapeutics. However, the precise ionic mechanisms involved in this control remain unclear. EXPERIMENTAL APPROACH: Cell imaging, patch-clamp electrophysiology and muscle tension recordings were used to define these mechanisms over a wide range of light stimulations. KEY RESULTS: Transgenic mice expressing a channelrhodopsin-2 variant [ChR2(H134R)] selectively in VSMCs were generated. Isolated VSMCs obtained from these mice demonstrated blue light-induced depolarizing whole-cell currents. Fine control of artery tone was attained by varying the intensity of the light stimulus. This arterial response was sufficient to overcome the endogenous, melanopsin-mediated, light-evoked, arterial relaxation observed in the presence of contractile agonists. Ca2+ entry through voltage-gated Ca2+ channels, and opening of plasmalemmal depolarizing channels (TMEM16A and TRPM) and intracellular IP3 receptors were involved in the ChR2(H134R)-dependent arterial response to blue light at intensities lower than ~0.1 mW·mm-2 . Light stimuli of greater intensity evoked a significant Ca2+ influx directly through ChR2(H134R) and produced marked intracellular alkalinization of VSMCs. CONCLUSIONS AND IMPLICATIONS: We identified the range of light intensity allowing optical control of arterial tone, primarily by means of endogenous channels and without substantial alteration to intracellular pH. Within this range, mice expressing ChR2(H134R) in VSMCs are a powerful experimental model for achieving accurate and tuneable optical voltage-clamp of VSMCs and finely graded control of arterial tone, offering new approaches to the discovery of vasorelaxant drugs.

Contrasting effects of phosphatidylinositol 4,5-bisphosphate on cloned TMEM16A and TMEM16B channels.

BACKGROUND AND PURPOSE: Ca2+ -activated Cl- channels (CaCCs) are gated open by a rise in intracellular Ca2+ concentration ([Ca2+ ]i ), typically provoked by activation of Gq -protein coupled receptors (Gq PCR). Gq PCR activation initiates depletion of plasmalemmal phosphatidylinositol 4,5-bisphosphate (PIP2 ). Here, we determined whether PIP2 acts as a signalling lipid for CaCCs coded by the TMEM16A and TMEM16B genes. EXPERIMENTAL APPROACH: Patch-clamp electrophysiology, in conjunction with genetically encoded systems to control cellular PIP2 content, was used to define the mechanism of action of PIP2 on TMEM16A and TMEM16B channels. KEY RESULTS: A water-soluble PIP2 analogue (diC8-PIP2 ) activated TMEM16A channels by up to fivefold and inhibited TMEM16B by ~0.2-fold. The effects of diC8-PIP2 on TMEM16A currents were especially pronounced at low [Ca2+ ]i . In contrast, diC8-PIP2 modulation of TMEM16B channels did not vary over a broad [Ca2+ ]i range but was only detectable at highly depolarized membrane potentials. Modulation of TMEM16A and TMEM16B currents was due to changes in channel gating, while single channel conductance was unaltered. Co-expression of TMEM16A or TMEM16B with a Danio rerio voltage-sensitive phosphatase (DrVSP), which degrades PIP2 , led to reduction and enhancement of TMEM16A and TMEM16B currents respectively. These effects were abolished by an inactivating mutation in DrVSP and antagonized by simultaneous co-expression of a phosphatidylinositol-4-phosphate 5-kinase that catalyses PIP2 formation. CONCLUSIONS AND IMPLICATIONS: PIP2 acts as a modifier of TMEM16A and TMEM16B channel gating. Drugs interacting with PIP2 signalling may affect TMEM16A and TMEM16B channel gating and have potential uses in basic science and implications for therapy.

Antiplatelet Therapy for Non-ST-Segment Elevation Myocardial Infarction in Complex "Real" Clinical Scenarios: A Consensus Document of the "Campania NSTEMI Study Group".

The incidence of ST-segment elevation myocardial infarction (STEMI) has significantly decreased. Conversely, the rate of non-STEMI (NSTEMI) has increased. Patients with NSTEMI have lower short-term mortality compared to patients with STEMI, whereas at long-term follow-up, the mortality becomes comparable. This might be due to the differences in baseline characteristics, including older age and a greater prevalence of comorbidities in the NSTEMI population. Although antithrombotic strategies used in patients with NSTEMI have been well studied in clinical trials and updated guidelines are available, patterns of use and outcomes in clinical practice are less well described. Thus, a panel of Italian cardiology experts assembled under the auspices of the "Campania NSTEMI Study Group" for comprehensive discussion and consensus development to provide practical recommendations, for both clinical and interventional cardiologists, regarding optimal management of antithrombotic therapy in patients with NSTEMI. This position article presents and discusses various clinical scenarios in patients with NSTEMI or unstable angina, including special subsets (eg, patients aged ≥85 years, patients with chronic renal disease or previous cerebrovascular events, and patients requiring triple therapy or long-term antithrombotic therapy), with the panel recommendations being provided for each scenario.

Work-related outcome after acute coronary syndrome: Implications of complex cardiac rehabilitation in occupational medicine.

OBJECTIVES: Coronary heart disease is frequent in the working-age population. Traditional outcomes, such as mortality and hospital readmission, are useful for evaluating prognosis. Fit-for-work is an emerging outcome with clinical as well as socioeconomic significance. We describe the possible benefit of a cardiac rehabilitation (CR) program for return to work (RTW) after acute coronary syndrome (ACS). MATERIAL AND METHODS: We evaluated 204 patients with recent ACS. They were divided into 4 groups on the basis of their occupational work load: very light (VL), light (L), moderate (M), and heavy (H). Work-related outcomes were assessed with the Work Performance Scale (WPS) of the Functional Status Questionnaire and as "days missed from work" (DMW) in the previous 4 weeks. The variables considered for outcomes were percent ejection fraction, functional capacity expressed in metabolic equivalents (METs), and participation or non-participation in the CR program (CR+ and CR-). RESULTS: One hundred thirty (66%) patients took part in the CR program. Total WPS scores for CR+ and CR- subgroups were VL group: 18±4 vs. 14±4 (p < 0.001), L group: 18±3 vs. 14±3 (p < 0.0001), M group: 19±3 vs. 16±3 (p < 0.003), and H group: 20±4 vs. 17±3 (p < 0.006). Fewer DMW were reported by the CR+ group. CONCLUSIONS: Non-participation in CR was a consistent cause of poorer work-related outcomes. Our findings indicate that CR and occupational counseling play a very important role in worker recovery and subsequent reintegration in the workplace, in particular among clerical workers.

Mechanism of allosteric activation of TMEM16A/ANO1 channels by a commonly used chloride channel blocker.

BACKGROUND AND PURPOSE: Calcium-activated chloride channels (CaCCs) play varied physiological roles and constitute potential therapeutic targets for conditions such as asthma and hypertension. TMEM16A encodes a CaCC. CaCC pharmacology is restricted to compounds with relatively low potency and poorly defined selectivity. Anthracene-9-carboxylic acid (A9C), an inhibitor of various chloride channel types, exhibits complex effects on native CaCCs and cloned TMEM16A channels providing both activation and inhibition. The mechanisms underlying these effects are not fully defined. EXPERIMENTAL APPROACH: Patch-clamp electrophysiology in conjunction with concentration jump experiments was employed to define the mode of interaction of A9C with TMEM16A channels. KEY RESULTS: In the presence of high intracellular Ca(2+) , A9C inhibited TMEM16A currents in a voltage-dependent manner by entering the channel from the outside. A9C activation, revealed in the presence of submaximal intracellular Ca(2+) concentrations, was also voltage-dependent. The electric distance of A9C inhibiting and activating binding site was ~0.6 in each case. Inhibition occurred according to an open-channel block mechanism. Activation was due to a dramatic leftward shift in the steady-state activation curve and slowed deactivation kinetics. Extracellular A9C competed with extracellular Cl(-) , suggesting that A9C binds deep in the channel's pore to exert both inhibiting and activating effects. CONCLUSIONS AND IMPLICATIONS: A9C is an open TMEM16A channel blocker and gating modifier. These effects require A9C to bind to a region within the pore that is accessible from the extracellular side of the membrane. These data will aid the future drug design of compounds that selectively activate or inhibit TMEM16A channels.

Disease-causing mutations associated with four bestrophinopathies exhibit disparate effects on the localization, but not the oligomerization, of Bestrophin-1.

BEST1 encodes Bestrophin-1 (Best1), a homo-oligomeric, integral membrane protein localized to the basolateral plasma membrane of the retinal pigment epithelium. Mutations in BEST1 cause five distinct retinal degenerative diseases, including adult vitelliform macular dystrophy (AVMD), autosomal recessive bestrophinopathy (ARB), autosomal dominant vitreoretinochoroidopathy (ADVIRC), and retinitis pigmentosa (RP). The mechanisms underlying these diseases and why mutations cause one disease over another are, for the most part, unknown. To gain insights into these four diseases, we expressed 28 Best1 mutants fused to YFP in polarized MDCK monolayers and, via confocal microscopy and immunofluorescence, live-cell FRET, and reciprocal co-immunoprecipitation experiments, screened these mutants for defects in localization and oligomerization. All 28 mutants exhibited comparable FRET efficiencies to and co-immunoprecipitated with WT Best1, indicating unimpaired oligomerization. RP- and ADVIRC-associated mutants were properly localized to the basolateral plasma membrane of cells, while two AVMD and most ARB mutants were mislocalized. When co-expressed, all mislocalized mutants caused mislocalization of WT Best1 to intracellular compartments. Our current and past results indicate that mislocalization of Best1 is not an absolute feature of any individual bestrophinopathy, occurring in AVMD, BVMD, and ARB. Furthermore, some ARB mutants that do not also cause dominant disease cause mislocalization of Best1, indicating that mislocalization is not a cause of disease, and that absence of Best1 activity from the plasma membrane is tolerated. Lastly, we find that the ARB truncation mutants L174Qfs*57 and R200X can form oligomers with WT Best1, indicating that the first ∼174 amino acids of Best1 are sufficient for oligomerization to occur.

A novel fluoroscopic method of measuring right-to-left interlead distance as a predictor of reverse left ventricular remodeling after cardiac resynchronization therapy.

PURPOSE: In spite of technological breakthroughs, the choice of a suitable location for the coronary sinus (CS) lead in biventricular implants is still mostly empiric. The aim of this study was to investigate the utility of a radiological index-the distance between the right ventricular (RV) and CS lead tips on fluoroscopic recordings, measured by means of a new method-as a tool for selecting the most profitable left ventricular (LV) lead position. METHODS: Forty-nine consecutive patients (36 male, 13female; mean age 63 ± 19 year), in whom the LV electrode was implanted in a lateral/postero-lateral position in the CS, were evaluated immediately after implantation. The fluoroscopic distances between the RV and LV lead tips were calculated off-line in antero-posterior (2DAP) and latero-lateral (2DLL) projections by means of integrated software. RESULTS: On 1-year follow-up evaluation, 53 % patients were classed as responders (R) (>15 % reduction in LV end-systolic volume) and 47 % as non-responders (NR). On receiver-operating curve analysis, 2DAP and 2DLL showed cut-off values of 81 mm and 51 mm, respectively. In discriminating between R and NR, 2DAP >81 mm displayed 95 % specificity and 74 % sensitivity, while 2DLL >51 mm displayed 74 % specificity and 92 % sensitivity. On multivariate analysis, the cut-off values of 2DAP and 2DLL were significantly predictive of R to CRT. CONCLUSIONS: In our single-center prospective experience, RV-LV interlead distance measured by means of a novel method on fluorographic recordings correlated with CRT response. The use of this method as an intra-operative guide to identifying suitable lead placement in the CS needs evaluating on-line and on a large scale.

Coronary spasm and acute myocardial infarction due to a mutation (V734I) in the nucleotide binding domain 1 of ABCC9.

BACKGROUND: Alterations in coronary vasomotor tone may participate in the pathogenesis of acute myocardial infarction (AMI). Vascular ATP-sensitive K(+) (KATP) channels, formed by Kir6.x/SUR2B, are key regulators of coronary tone and mutations in cardiac (Kir6.2/SUR2A) KATP channels result in heart disease. Here we explore the pathophysiological mechanism of a rare mutation (V734I) found in exon 17 of the ABCC9 gene, estimated to cause a 6.4-fold higher risk of AMI before the age of 60. METHODS AND RESULTS: Eleven patients carrying the mutation were identified; they presented AMI of vasospastic origin associated with increased plasma levels of endothelin-1 and increased leukocyte ROCK activity. The effects of the mutation on the functional properties of the two splice variants of ABCC9 (SUR2A and SUR2B) were studied using patch-clamp electrophysiology. The mutation reduced the sensitivity to MgATP inhibition of Kir6.2/SUR2B channels but not of Kir6.2/SUR2A and Kir6.1/SUR2B channels. Furthermore, the stimulatory effects of MgNDP (MgADP, MgGDP and MgUDP) were unaltered in mutant Kir6.2/SUR2A and Kir6.1/SUR2B channels. In contrast, mutant channels composed of Kir6.2 and SUR2B were less sensitive to MgNDP activation, assessed in the presence of MgATP. The antianginal drug nicorandil activated Kir6.2/SUR2B-V734I channels, thus substituting for the loss of MgNDP stimulation, suggesting that this drug could be of therapeutic use in the treatment of AMI associated with V734I. CONCLUSIONS: The 734I allele in ABCC9 may influence susceptibility to AMI by impairing the response of vascular, but not cardiac, KATP channels to intracellular nucleotides. This is the first human mutation in an ion channel gene to be implicated in AMI.