Early results of a surgeon-led, perioperative surgical home.

BACKGROUND: The Perioperative Surgical Home is a novel care model designed to provide patient-centered, high-quality surgical care. In 2013, we implemented POSH, a pilot Peri-Operative Surgical Home at Phoenix Indian Medical Center (PIMC), an Indian Health Service hospital, as a quality improvement project. After 2 y, we sought to quantify the impact of POSH on the quality of surgical care at PIMC. MATERIALS AND METHODS: We conducted a retrospective review of 33 surgical patients who underwent surgery at PIMC through the POSH process between 2013 and 2015 matched to 64 historical controls with similar operations. Study patients underwent surgery via the POSH treatment process. Primary outcomes were composite measures of (1) care standards and (2) care goals. Success was defined as meeting seven of nine care standards and six of eight care goals. RESULTS AND DISCUSSION: The mean number of care standards met was 8.1 ± 1.0 versus 4.2 ± 1.4 (P < 0.001) and the mean number of care goals met was 6.7 ± 0.8 versus 6.1 ± 1.1 (P = 0.005) for POSH patients and historical controls, respectively. Patients participating in the POSH model were 8.6 (95% confidence interval: 3.5-22.3) and 1.5 (95% confidence interval: 1.2-1.9) times more likely to meet the minimum number of care standards and goals, respectively. Fourteen of the study patients (42%) would not have been offered surgery at PIMC before POSH due to elevated surgical risk. CONCLUSIONS: POSH may have improved quality of surgical care at PIMC while expanding services to more complex patients. POSH may present an opportunity for improved surgical quality in resource-constrained environments.

Biodesign of a renal-protective peptide based on alternative splicing of B-type natriuretic peptide.

Alternative RNA splicing may provide unique opportunities to identify drug targets and therapeutics. We identified an alternative spliced transcript for B-type natriuretic peptide (BNP) resulting from intronic retention. This transcript is present in failing human hearts and is reduced following mechanical unloading. The intron-retained transcript would generate a unique 34 amino acid (aa) carboxyl terminus while maintaining the remaining structure of native BNP. We generated antisera to this carboxyl terminus and identified immunoreactivity in failing human heart tissue. The alternatively spliced peptide (ASBNP) was synthesized and unlike BNP, failed to stimulate cGMP in vascular cells or vasorelax preconstricted arterial rings. This suggests that ASBNP may lack the dose-limiting effects of recombinant BNP. Given structural considerations, a carboxyl-terminal truncated form of ASBNP was generated (ASBNP.1) and was determined to retain the ability of BNP to stimulate cGMP in canine glomerular isolates and cultured human mesangial cells but lacked similar effects in vascular cells. In a canine-pacing model of heart failure, systemic infusion of ASBNP.1 did not alter mean arterial pressure but increased the glomerular filtration rate (GFR), suppressed plasma renin and angiotensin, while inducing natriuresis and diuresis. Consistent with its distinct in vivo effects, the activity of ASBNP.1 may not be explained through binding and activation of NPR-A or NPR-B. Thus, the biodesigner peptide ASBNP.1 enhances GFR associated with heart failure while lacking the vasoactive properties of BNP. These findings demonstrate that peptides with unique properties may be designed based on products of alternatively splicing.

Thoracic endovascular aortic repair of an aberrant right subclavian artery: technique and long-term outcome.

BACKGROUND: Aberrant right subclavian artery (ARSA) is the most common congenital arch anomaly, which can be complicated by aneursymal dilation at its ostium. We describe a successful repair of an ARSA with a three-stage operative procedure using a left carotid to subclavian bypass, coiling of the ARSA, and thoracic endovascular aortic repair with long-term clinical and radiographic follow-up.

Pharmacodynamics of a novel designer natriuretic peptide, CD-NP, in a first-in-human clinical trial in healthy subjects.

CD-NP is a novel chimeric natriuretic peptide (NP) consisting of the 22-amino-acid (AA) human C-type natriuretic peptide (CNP), a venodilating peptide with limited renal actions and minimal effects on blood pressure, and the 15-AA C-terminus of Dendroaspis NP (DNP). The rationale for the design of CD-NP was to enhance the renal actions of CNP, the ligand for natriuretic peptide receptor-B, but without inducing excessive hypotension. Here we report the first-in-human studies for CD-NP, which represent the first successful clinical testing of a chimeric NP demonstrating in normal human volunteers that CD-NP possesses cyclic guanosine monophosphate-activating, natriuretic, and aldosterone-suppressing properties without inducing excessive hypotension, laying the foundation for additional studies on this first-in-class new cardiovascular therapeutic in human heart failure, which are now underway worldwide.

Designer natriuretic peptides.

Designer natriuretic peptides (NPs) are novel hybrid peptides that are engineered from the native NPs through addition, deletion, or substitution of amino acid(s) with a goal toward optimization of pharmacological actions while minimizing undesirable effects. In this article, selected peptides that were designed in our laboratory are reviewed, and future directions for research and development of designer NPs are discussed.

Human betaine-homocysteine methyltransferase (BHMT) and BHMT2: common gene sequence variation and functional characterization.

Betaine-homocysteine methyltransferase (BHMT) catalyzes the remethylation of homocysteine. BHMT2 encodes a protein 73% identical in amino acid sequence to BHMT, but the function of BHMT2 remains unclear. We set out to identify and functionally characterize common genetic variation in BHMT and BHMT2. Specifically, we sequenced exons, exon-intron splice junctions and the 5'-flanking regions (5'-FRs) of BHMT and BHMT2 using 240 DNA samples from four ethnic groups. Twenty-five single nucleotide polymorphisms (SNPs), including 4 nonsynonymous SNPs, and 39 SNPs, including 4 nonsynonymous, were observed in BHMT and BHMT2, respectively. BHMT wild type (WT) and variant allozymes were expressed in COS-1 cells. Variant allozymes showed no significant differences from WT in levels of enzyme activity or immunoreactive protein, but there were statistically significant differences in apparent K(m) values. Luciferase reporter gene constructs were created for the three most common BHMT 5'-FR haplotypes, and significant variation was observed in the ability of these constructs to drive transcription. Although BHMT2 mRNA has been observed in human liver and kidney, expression of the protein has not been reported. We were unable to express BHMT2 in mammalian cells, and the protein aggregated after bacterial expression. Furthermore, BHMT2 was rapidly degraded in a rabbit reticulocyte lysate, but it could be stabilized by cotransfection of COS-1 cells with BHMT and, after cotransfection, it coprecipitated with BHMT. These studies have defined common genetic variation in BHMT and BHMT2 and functionally characterized BHMT SNPs. They may also help to explain why BHMT2 has not previously been defined functionally.

A Human Study to Evaluate Safety, Tolerability, and Cyclic GMP Activating Properties of Cenderitide in Subjects With Stable Chronic Heart Failure.

Cenderitide is a novel designer natriuretic peptide (NP) composed of C-type natriuretic peptide (CNP) fused to the C-terminus of Dendroaspis natriuretic peptide (DNP). Cenderitide was engineered to coactivate the two NP receptors, particulate guanylyl cyclase (pGC)-A and -B. The rationale for its design was to achieve the renal-enhancing and antifibrotic properties of dual receptor activation, but without clinically significant hypotension. Here we report the first clinical trial on the safety, tolerability, and cyclic guanosine monophosphate (cGMP) activating properties of Cenderitide in subjects with stable heart failure (HF). Four-hour infusion of Cenderitide was safe, well-tolerated, and significantly increased plasma cGMP levels and urinary cGMP excretion without adverse effects with no change in blood pressure. Thus, Cenderitide has a favorable safety profile and expected pharmacological effects in stable human HF. Our results support further investigations of Cenderitide in HF as a potential future cGMP-enhancing therapeutic strategy.

Beneficial Effects of Reconstituted High-Density Lipoprotein (rHDL) on Circulating CD34+ Cells in Patients after an Acute Coronary Syndrome.

BACKGROUND: High-density lipoproteins (HDL) favorably affect endothelial progenitor cells (EPC). Circulating progenitor cell level and function are impaired in patients with acute coronary syndrome (ACS). This study investigates the short-term effects of reconstituted HDL (rHDL) on circulating progenitor cells in patients with ACS. METHODS AND FINDINGS: The study population consisted of 33 patients with recent ACS: 20 patients from the ERASE trial (randomized to receive 4 weekly intravenous infusions of CSL-111 40 mg/kg or placebo) and 13 additional patients recruited as controls using the same enrolment criteria. Blood was collected from 16 rHDL (CSL-111)-treated patients and 17 controls at baseline and at 6-7 weeks (i.e. 2-3 weeks after the fourth infusion of CSL-111 in ERASE). CD34+ and CD34+/kinase insert domain receptor (KDR+) progenitor cell counts were analyzed by flow cytometry. We found preserved CD34+ cell counts in CSL-111-treated subjects at follow-up (change of 1.6%), while the number of CD34+ cells was reduced (-32.9%) in controls (p = 0.017 between groups). The level of circulating SDF-1 (stromal cell-derived factor-1), a chemokine involved in progenitor cell recruitment, increased significantly (change of 21.5%) in controls, while it remained unchanged in CSL-111-treated patients (p = 0.031 between groups). In vitro exposure to CSL-111 of early EPC isolated from healthy volunteers significantly increased CD34+ cells, reduced early EPC apoptosis and enhanced their migration capacity towards SDF-1. CONCLUSIONS: The relative increase in circulating CD34+ cells and the low SDF-1 levels observed following rHDL infusions in ACS patients point towards a role of rHDL in cardiovascular repair mechanisms.

Cenderitide: structural requirements for the creation of a novel dual particulate guanylyl cyclase receptor agonist with renal-enhancing in vivo and ex vivo actions.

AIMS: Cenderitide is a novel dual natriuretic peptide (NP) receptor chimeric peptide activator, which targets the particulate guanylyl cyclase B (pGC-B) receptor and pGC-A unlike native NPs. Cenderitide was engineered to retain the anti-fibrotic properties of C-type natriuretic peptide (CNP)/pGC-B with renal-enhancing actions facilitated by fusion to the carboxyl terminus of Dendroaspis NP (DNP), a pGC-A agonist, to CNP. Here, we address significance of the DNP carboxyl terminus in dual pGC receptor activation and actions of cenderitide compared with CNP on renal function and cyclic guanosine monophosphate (cGMP) in vivo and ex vivo in normal canines. METHODS AND RESULTS: In vitro, only cenderitide and not CNP or three CNP-based variants was a potent dual pGC-A/pGC-B activator of cGMP production (from 5 to 237 pmol/mL) in human embryonic kidney (HEK) 293 cells overexpressing human pGC-A while in pGC-B overexpressing cells cenderitide increased cGMP production (from 4 to 321 pmol/mL) while the three CNP-based variants were weak agonists. Based upon our finding that the DNP carboxyl terminus is a key structural requirement for dual pGC-A/pGC-B activation, we defined in vivo the renal-enhancing actions of cenderitide compared with CNP. Cenderitide increased urinary cGMP excretion (from 989 to 5977 pmol/mL), net generation of renal cGMP (821-4124 pmol/min), natriuresis (12-242 µEq/min), and glomerular filtration rate (GFR) (37-51 mL/min) while CNP did not. We then demonstrated the transformation of CNP ex vivo into a renal cGMP-activating peptide which increased cGMP in freshly isolated glomeruli eight-fold greater than CNP. CONCLUSION: The current study establishes that dual pGC-A and pGC-B activation with CNP requires the specific carboxyl terminus of DNP. In normal canines in vivo and in glomeruli ex vivo, the carboxyl terminus of DNP transforms CNP into a natriuretic and GFR-enhancing peptide. Future studies of cenderitide are warranted in cardiorenal disease states to explore its efficacy in overall cardiorenal homeostasis.

Therapeutic potential of novel Na+-Ca2+ exchange inhibitors in attenuating ischemia-reperfusion injury.

The cardiac Na+-Ca2+ exchanger (NCX) plays an essential role in regulating Ca2+ under physiological and pathophysiological conditions. In its forward mode of operation, which predominates under physiological conditions, it extrudes the Ca2+ that enters the cardiac myocyte on a beat-to-beat basis. During ischemia and reperfusion, increased intracellular Na+ leads to a decrease in Ca2+ efflux and enhanced Ca2+ influx via the NCX, potentially leading to Ca2+ overload, which is one of the major pathophysiological mechanisms for ischemia-reperfusion injury. Novel NCX inhibitors discovered in recent years have shown great promise in attenuating ischemia-reperfusion injury.

The incidence and prognosis of Brugada electrocardiographic pattern in the Manitoba Follow-Up Study.

BACKGROUND: There is a paucity of long-term follow-up data on individuals with asymptomatic Brugada electrocardiographic (ECG) pattern. OBJECTIVES: To investigate the incidence and prognosis of spontaneous Brugada ECG pattern in a prospective cohort. METHODS: The Manitoba Follow-up Study is Canada's longest-running study of cardiovascular disease. Since 1948, a cohort of 3983 healthy aircrew recruits has been followed with routine medical examination, including ECG. Over a 55-year follow-up period, clinical and ECG assessments were performed every three to five years, with yearly contact to monitor vital status. The mean age of the cohort at entry and the average age of the 1375 survivors in 2003 were 31 and 83 years of age, respectively. Brugada ECG pattern was defined as ST-segment elevation in at least one of leads V1 to V3 with a J wave amplitude of at least 2 mm, negative T waves, generally coved ST-T configuration, in the absence of alternative explanations. Serial ECGs of 273 subjects (6.9% of the cohort) with complete right bundle branch block at any time during follow-up were reviewed. Follow-up records pertaining to clinical course were also reviewed. RESULTS: All ECGs (in total 5665) from this cohort were reviewed. Four men had intermittent Brugada ECG pattern (lifetime incidence one per 1000): three men (all 80 years of age or older) were well on last follow-up and one had died of Alzheimer's disease. None of these men had syncope or ventricular arrhythmias documented during follow-up. CONCLUSIONS: The longevity of asymptomatic individuals in this cohort was not affected by spontaneous Brugada ECG pattern.

Can structured clinical assessment using modified Duke's criteria improve appropriate use of echocardiography in patients with suspected infective endocarditis?

BACKGROUND: Although echocardiography has been incorporated into the diagnostic algorithm of patients with suspected infective endocarditis, systematic usage in clinical practice remains ill defined. OBJECTIVE: To test whether the rigid application of a predefined standardized clinical assessment using the Duke criteria by the research team would provide improved diagnostic accuracy of endocarditis when compared with usual clinical care provided by the attending team. METHODS: Between April 1, 2000 and March 31, 2001, 101 consecutive inpatients with suspected endocarditis were examined prospectively and independently by both teams. The clinical likelihood of endocarditis was graded as low, moderate or high. All patients underwent transthoracic echocardiography and appropriate transesophageal echocardiography if deemed necessary. All diagnostic and therapeutic outcomes were evaluated prospectively. RESULTS: Of 101 consecutive inpatients (age 50+/-16 years; 62 males) enrolled, 22% subsequently were found to have endocarditis. The pre-echocardiographic likelihood categories as graded by the clinical and research teams were low in nine and 37 patients, respectively, moderate in 83 and 40 patients, respectively, and high in nine and 24 patients, respectively, with only a marginal agreement in classification (kappa=0.33). Of the 37 patients in the low likelihood group and 40 in the intermediate group, no endocarditis was diagnosed. In 22 of 24 patients classified in the high likelihood group, there was echocardiographic evidence of vegetations suggestive of endocarditis. Discriminating factors that increased the likelihood of endocarditis were a prior history of valvular disease, the presence of an indwelling catheter, positive blood cultures, and the presence of a new murmur and a vascular event. General internists, rheumatologists and intensive care physicians were more likely to order echocardiography in patients with low clinical probability of endocarditis, of which pneumonia was the most common alternative diagnosis. CONCLUSION: Although prediction of clinical likelihood varies between observers, endocarditis is generally found only in those individuals with a moderate to high pre-echocardiographic clinical likelihood. Strict adherence to indications for transthoracic echocardiography and transesophageal echocardiography may help to facilitate more accurate diagnosis within the moderate likelihood category. Patients with low likelihood do not derive additional diagnostic benefit with echocardiography although other factors such as physician reassurance may continue to drive diagnostic demand.

Integrin α9ß1 in airway smooth muscle suppresses exaggerated airway narrowing.

Exaggerated contraction of airway smooth muscle is the major cause of symptoms in asthma, but the mechanisms that prevent exaggerated contraction are incompletely understood. Here, we showed that integrin α9ß1 on airway smooth muscle localizes the polyamine catabolizing enzyme spermidine/spermine N1-acetyltransferase (SSAT) in close proximity to the lipid kinase PIP5K1γ. As PIP5K1γ is the major source of PIP2 in airway smooth muscle and its activity is regulated by higher-order polyamines, this interaction inhibited IP3-dependent airway smooth muscle contraction. Mice lacking integrin α9ß1 in smooth muscle had increased airway responsiveness in vivo, and loss or inhibition of integrin α9ß1 increased in vitro airway narrowing and airway smooth muscle contraction in murine and human airways. Contraction was enhanced in control airways by the higher-order polyamine spermine or by cell-permeable PIP2, but these interventions had no effect on airways lacking integrin α9ß1 or treated with integrin α9ß1-blocking antibodies. Enhancement of SSAT activity or knockdown of PIP5K1γ inhibited airway contraction, but only in the presence of functional integrin α9ß1. Therefore, integrin α9ß1 appears to serve as a brake on airway smooth muscle contraction by recruiting SSAT, which facilitates local catabolism of polyamines and thereby inhibits PIP5K1γ. Targeting key components of this pathway could thus lead to new treatment strategies for asthma.

ApoA-1 infusion reduces arterial cholesterol and myocardial lesions in a rat model of cardiac dysfunction and insulin resistance.

OBJECTIVE: Low plasma high-density lipoprotein cholesterol (HDL-C) concentration is associated with the metabolic syndrome (MetS) and increased prevalence of cardiovascular disease (CVD). Animal and human studies report infusion of apolipoprotein A-1 (apoA-1) can reduce endothelial dysfunction, and/or induce regression of atherosclerosis. However, the direct mechanisms underlying the vascular benefits of either apoA-1 or HDL-C remain unclear. In this study, we assessed the ability of reconstituted HDL (rHDL) to improve vascular complications of MetS, including left ventricular (LV)-hypertrophy, arterial cholesterol deposition and myocardial lesion development. METHODS AND RESULTS: Obese insulin resistant (IR) JCR:LA-cp rats were infused with rHDL (0.4 mg/kg) over 3 days before assessing cardiac function (Echocardiography) at days 7 and 50 post-infusion, as well as haematoxylin and eosin staining of myocardial lesions at day 50. Acute ex vivo arterial cholesterol deposition was assessed with acute infusion of rHDL ex-vivo. Infusion of rHDL partially corrected abnormal diastolic compliance (18%; *p<0.05) and improved parameters of cardiac function in IR rats. Further, acute rHDL infusion in carotid vessels reduced remnant lipoprotein associated-cholesterol deposition (30-86%; **p<0.01) ex vivo in IR and male Wistar rats and reduced (41%; *p<0.05) the frequency of early-stage myocardial lesions in IR rats. CONCLUSION: Short-term infusion of rHDL may beneficially reduce chronic vascular sequelae of MetS, including temporary improvement in LV-dysfunction, acute reduction of acute arterial cholesterol deposition and the development of early-stage myocardial lesions in the JCR:LA-cp rat.

Digoxin toxicity precipitated by clarithromycin use: case presentation and concise review of the literature.

We present a case of digoxin toxicity in the context of dehydration, renal dysfunction and concomitant use of the macrolide antibiotic, clarithromycin, which is known to inhibit P-glycoprotein-mediated efflux mechanisms of digoxin. A focused review of the literature is presented. Health care providers need to be vigilant of this mechanism of drug-drug interaction, which is also relevant to other commonly used cardiovascular drugs.

A pilot study of paternal drug exposure: the Motherisk experience.

BACKGROUND: There is a dearth of information on paternal drug exposure at the time of conception. The Motherisk Program, established in 1985, is a teratology information and clinical consultation service on drug safety during pregnancy and lactation, as well as paternal exposure (PEx). Here, we reviewed for the first time our experience with PEx. METHODS: This was an observational retrospective cohort study using a prospectively collected database. Telephone counselling records from January 2002 to December 2007, inclusive, were screened to identify cases concerning PEx. RESULTS: Of a total of 188,188 counselling requests over these 6 years, 301 (0.16%) pertained to PEx. Counselling was most frequently sought on methotrexate, finasteride, prednisone and azathioprine. For many drugs, limited or no information was available on PEx. CONCLUSIONS: Paternal exposure represents a small fraction of counselling requests to Motherisk. Our findings suggest that there is an ongoing need for information on paternal drug exposure.

A novel chimeric natriuretic peptide reduces cardiomyocyte hypertrophy through the NHE-1-calcineurin pathway.

AIMS: Natriuretic peptides (NPs) inhibit cardiomyocyte hypertrophy through a cyclic GMP (cGMP)-dependent process, although these effects are associated with substantial vasodilatation. In this study, we used CU-NP, a non-vasodilatating novel NP synthesized from the ring structure of human C-type NP (CNP) and both C- and N-termini of urodilatin, and investigated whether it can directly modulate cardiomyocyte hypertrophy. METHODS AND RESULTS: Experiments were carried out in cultured neonatal rat ventricular myocytes exposed to phenylephrine, angiotensin II, or endothelin-1 in the absence or presence of CU-NP. CU-NP produced a concentration- and time-dependent increase in intracellular cGMP levels. The hypertrophic responses to all agonists were abrogated by 10 nM CU-NP. CU-NP treatment also prevented increased activity, gene and protein expression of sodium-hydrogen exchanger-1 (NHE-1) as well as elevations in intracellular Na(+) concentrations caused by hypertrophic agents. In addition, these effects were associated with a more than two-fold increase in activity of the Ca(2+)-dependent protein phosphatase calcineurin that peaked 6 h after addition of hypertrophic stimuli. Early (1-3 h) calcineurin activation was unaffected by CU-NP, although activation at 6 and 24 h was prevented by CU-NP as was the resultant translocation of the transcriptional factor NFAT into nuclei. CONCLUSION: Our study demonstrates a direct anti-hypertrophic effect of the chimeric peptide CU-NP via NHE-1 inhibition, thereby preventing calcineurin activation and NFAT nuclear import. Thus, CU-NP represents a novel fusion peptide of CNP and urodilatin that has the potential to be developed into a therapeutic agent to treat cardiac hypertrophy and heart failure.

Unusual reactions to 5-HT3 receptor antagonists in a child with rhabdomyosarcoma.

A case of unusual reactions consisting of involuntary abnormal facial movements in a child following exposure to the 5-HT3 receptor antagonists for prophylaxis against chemotherapy-induced vomiting is presented. Potential mechanisms for these reactions are discussed.

EUR-1008 pancreatic enzyme replacement is safe and effective in patients with cystic fibrosis and pancreatic insufficiency.

BACKGROUND: EUR-1008 (Zenpep [pancrelipase]) is a new, enteric-coated, porcine-derived pancreatic enzyme product (PEP) developed for the treatment of cystic fibrosis (CF) patients with malabsorption associated with exocrine pancreatic insufficiency (EPI). Unlike currently marketed PEPs, EUR-1008 contains the label-claimed lipase content. Safety and efficacy were assessed in younger (<7 years) and older (> or =7 years) CF patients with EPI. METHODS: Two multicenter studies were conducted: a randomized, double-blind, placebo-controlled, crossover trial in patients > or =7 years of age (N=34) and a supplemental, open-label study in children <7 years of age (N=19). Use of any medications altering gastric pH/motility was prohibited during the studies. Outcome measures in the randomized trial included changes in the coefficient of fat absorption (CFA), coefficient of nitrogen absorption (CNA), and signs/symptoms of malabsorption for EUR-1008 vs. placebo. Outcome measures in the supplemental study included safety and response (defined as no steatorrhea and no overt signs/symptoms of malabsorption) to EUR-1008 vs. previous enzyme treatment. RESULTS: In the randomized trial, EUR-1008 treatment compared to placebo resulted in a significantly higher mean CFA (88.3% vs. 62.8%, respectively) and CNA (87.2% vs. 65.7%, respectively) (both p<0.001) and reduced the incidence of malabsorption signs and symptoms in 32 evaluable patients. In the supplemental study, 11 of 19 patients met the criteria for responder with EUR-1008 at the end of the study vs. 10 of 19 patients at screening (previous PEP), and improvements in clinical symptoms were reported with EUR-1008 treatment. EUR-1008 was safe and well tolerated, and no serious drug-related AEs were reported in either study. CONCLUSIONS: EUR-1008 was safe, well tolerated, and effective in CF patients of all ages with EPI-associated malabsorption in two clinical trials. Treatment led to clinically and statistically significant improvements in CFA and CNA in the randomized study, and control of malabsorption and clinical symptoms in both studies.

Myocardial alterations in senescent mice and effect of exercise training: a strain rate imaging study.

BACKGROUND: Aging is accompanied by an alteration in myocardial contractility. However, its noninvasive detection is difficult. The effect of chronic exercise on this decrease is unknown. Murine models of senescence are increasingly used to test therapies in aging. We tested whether strain rate imaging detected left ventricular (LV) systolic dysfunction in aging mice and was able to assess a potential improvement after exercise. METHODS AND RESULTS: Young (3 weeks), adult (2 to 3 months), and old (6 to 18 months) C57BL6 male mice underwent echocardiograms with strain rate imaging, either in sedentary conditions or before, 2 weeks and 4 weeks after chronic swimming. Hemodynamic parameters of LV function including maximal and end-systolic elastance were obtained before euthanizing. LV fibrosis was measured using Sirius red staining. Conventional echocardiography was unable to detect LV systolic dysfunction in old mice, whereas both systolic strain rate and load-independent hemodynamic parameters such as preload recruitable stroke work and end-systolic elastance were significantly decreased. Both strain rate and load-independent hemodynamic parameters normalized after 4 weeks of exercise. Both endocardial and epicardial fibrosis were increased in the LV of aging mice. Endocardial fibrosis decreased in exercised aged mice. CONCLUSIONS: Strain rate noninvasively detects LV systolic dysfunction associated with aging in mice, whereas conventional echocardiography does not. Chronic exercise normalizes LV systolic function and decreases fibrosis in old mice. Strain rate imaging in mice may be a useful tool to monitor the effect of new therapeutic strategies preventing the myocardial dysfunction associated with aging.