Radovits T, Oláh A, Lux Á, Németh BT, Hidi L, Birtalan E, Kellermayer D, Mátyás C, Szabó G, Merkely B. Rat model of exercise-induced cardiac hypertrophy: hemodynamic characterization using left ventricular pressure-volume analysis. Am J Physiol Heart Circ Physiol 305: H124 -H134, 2013. First published May 3, 2013 doi:10.1152/ajpheart.00108.2013.-Long-term exercise training is associated with characteristic structural and functional changes of the myocardium, termed athlete's heart. Several research groups investigated exercise training-induced left ventricular (LV) hypertrophy in animal models; however, only sporadic data exist about detailed hemodynamics. We aimed to provide functional characterization of exercise-induced cardiac hypertrophy in a rat model using the in vivo method of LV pressure-volume (P-V) analysis. After inducing LV hypertrophy by swim training, we assessed LV morphometry by echocardiography and performed LV P-V analysis using a pressureconductance microcatheter to investigate in vivo cardiac function. Echocardiography showed LV hypertrophy (LV mass index: 2.41 Ϯ 0.09 vs. 2.03 Ϯ 0.08 g/kg, P Ͻ 0.01), which was confirmed by heart weight data and histomorphometry. Invasive hemodynamic measurements showed unaltered heart rate, arterial pressure, and LV enddiastolic volume along with decreased LV end-systolic volume, thus increased stroke volume and ejection fraction (73.7 Ϯ 0.8 vs. 64.1 Ϯ 1.5%, P Ͻ 0.01) in trained versus untrained control rats. The P-V loop-derived sensitive, load-independent contractility indexes, such as slope of end-systolic P-V relationship or preload recruitable stroke work (77.0 Ϯ 6.8 vs. 54.3 Ϯ 4.8 mmHg, P ϭ 0.01) were found to be significantly increased. The observed improvement of ventriculoarterial coupling (0.37 Ϯ 0.02 vs. 0.65 Ϯ 0.08, P Ͻ 0.01), along with increased LV stroke work and mechanical efficiency, reflects improved mechanoenergetics of exercise-induced cardiac hypertrophy. Despite the significant hypertrophy, we observed unaltered LV stiffness (slope of end-diastolic P-V relationship: 0.043 Ϯ 0.007 vs. 0.040 Ϯ 0.006 mmHg/l) and improved LV active relaxation (: 10.1 Ϯ 0.6 vs. 11.9 Ϯ 0.2 ms, P Ͻ 0.01). According to our knowledge, this is the first study that provides characterization of functional changes and hemodynamic relations in exercise-induced cardiac hypertrophy.exercise-induced cardiac hypertrophy; pressure-volume analysis; systolic function; diastolic function; cardiac mechanoenergetics ATHLETE'S HEART HAS BEEN DESCRIBED as the complex structural, functional, and electrical cardiac remodeling induced by longterm exercise training (40). Exercise training-induced cardiac hypertrophy is an important physiological adaption, which includes balanced increase of left ventricular (LV) and left atrial diameters, cardiac mass, and LV wall thicknesses effected by myocyte hypertrophy and neoangiogenesis (10,12,25,36,37).Cardiac enlargement in athletes has been reported since the late 1890s (6), and several aspects of athlete's heart have been intensively inv...

function is considered to be precisely measurable only by invasive hemodynamics. We aimed to correlate strain values measured by speckle-tracking echocardiography (STE) with sensitive contractility parameters of pressure-volume (P-V) analysis in a rat model of exercise-induced left ventricular (LV) hypertrophy. LV hypertrophy was induced in rats by swim training and was compared with untrained controls. Echocardiography was performed using a 13-MHz linear transducer to obtain LV long-and short-axis recordings for STE analysis (GE EchoPAC). Global longitudinal (GLS) and circumferential strain (GCS) and longitudinal (LSr) and circumferential systolic strain rate (CSr) were measured. LV P-V analysis was performed using a pressure-conductance microcatheter, and load-independent contractility indices [slope of the end-systolic P-V relationship (ESPVR), preload recruitable stroke work (PRSW), and maximal dP/dt-enddiastolic volume relationship (dP/dtmax-EDV)] were calculated. Trained rats had increased LV mass index (trained vs. control; 2.76 Ϯ 0.07 vs. 2.14 Ϯ 0.05 g/kg, P Ͻ 0.001). P-V loop-derived contractility parameters were significantly improved in the trained group (ESPVR: 3.58 Ϯ 0.22 vs. 2.51 Ϯ 0.11 mmHg/ l; PRSW: 131 Ϯ 4 vs. 104 Ϯ 2 mmHg, P Ͻ 0.01). Strain and strain rate parameters were also supernormal in trained rats (GLS: Ϫ18.8 Ϯ 0.3 vs. Ϫ15.8 Ϯ 0.4%; LSr: Ϫ5.0 Ϯ 0.2 vs. Ϫ4.1 Ϯ 0.1 Hz; GCS: Ϫ18.9 Ϯ 0.8 vs. Ϫ14.9 Ϯ 0.6%; CSr: Ϫ4.9 Ϯ 0.2 vs. Ϫ3.8 Ϯ 0.2 Hz, P Ͻ 0.01). ESPVR correlated with GLS (r ϭ Ϫ0.71) and LSr (r ϭ Ϫ0.53) and robustly with GCS (r ϭ Ϫ0.83) and CSr (r ϭ Ϫ0.75, all P Ͻ 0.05). PRSW was strongly related to GLS (r ϭ Ϫ0.64) and LSr (r ϭ Ϫ0.71, both P Ͻ 0.01). STE can be a feasible and useful method for animal experiments. In our rat model, strain and strain rate parameters closely reflected the improvement in intrinsic contractile function induced by exercise training. speckle-tracking echocardiography; pressure-volume analysis; athlete's heart; contractility; strain LONG-TERM EXERCISE TRAINING induces physiological left ventricular (LV) hypertrophy, a molecular and cellular growth process of the heart in response to altered loading conditions (6). In contrast to pathological hypertrophy, this adaptation leads to maintained or even enhanced cardiac function (2, 14). Hemodynamic changes of exercise-induced hypertrophy were characterized by our research group in a rat model, focusing also on the improved LV inotropic state (23). Contractility is the intrinsic ability of the myocardium to generate force and to shorten independently of changes in preload or afterload with fixed heart rates. In the past few decades, efforts have been made to transfer the physiological concept of contractility to the intact beating heart (4).Pressure-volume (P-V) analysis recently became the gold standard to investigate in vivo hemodynamics in animal models. During preload reduction maneuvers such as gradual occlusion of vena cava inferior, load-independent indices of myocardial contractility could be obtained (20). Th...

AimsHeart failure with preserved ejection fraction (HFpEF) has a great epidemiological burden. The pathophysiological role of cyclic guanosine monophosphate (cGMP) signalling has been intensively investigated in HFpEF. Elevated levels of cGMP have been shown to exert cardioprotective effects in various cardiovascular diseases, including diabetic cardiomyopathy. We investigated the effect of long‐term preventive application of the phosphodiesterase‐5A (PDE5A) inhibitor vardenafil in diabetic cardiomyopathy‐associated HFpEF.Methods and resultsZucker diabetic fatty (ZDF) rats were used as a model of HFpEF and ZDF lean rats served as controls. Animals received vehicle or 10 mg/kg body weight vardenafil per os from weeks 7 to 32 of age. Cardiac function, morphology was assessed by left ventricular (LV) pressure–volume analysis and echocardiography at week 32. Cardiomyocyte force measurements were performed. The key markers of cGMP signalling, nitro‐oxidative stress, apoptosis, myocardial hypertrophy and fibrosis were examined. The ZDF animals showed diastolic dysfunction (increased LV/cardiomyocyte stiffness, prolonged LV relaxation time), preserved systolic performance, decreased myocardial cGMP level coupled with impaired protein kinase G (PKG) activity, increased nitro‐oxidative stress, enhanced cardiomyocyte apoptosis, and hypertrophic and fibrotic remodelling of the myocardium. Vardenafil effectively prevented the development of HFpEF by maintaining diastolic function (decreased LV/cardiomyocyte stiffness and LV relaxation time), by restoring cGMP levels and PKG activation, by lowering apoptosis and by alleviating nitro‐oxidative stress, myocardial hypertrophy and fibrotic remodelling.ConclusionsWe report that vardenafil successfully prevented the development of diabetes mellitus‐associated HFpEF. Thus, PDE5A inhibition as a preventive approach might be a promising option in the management of HFpEF patients with diabetes mellitus.

Excessive physical activity has an adverse effect on the heart. The observed functional impairment is associated with increased nitro-oxidative stress, enhanced apoptotic signaling and dysregulation of the matrix metalloproteinase system after exhaustive exercise.

Left ventricular (LV) hypertrophy is a physiological or pathological response of LV myocardium to increased cardiac load. We aimed at investigating and comparing hemodynamic alterations in well-established rat models of physiological hypertrophy (PhyH) and pathological hypertrophy (PaH) by using LV pressure-volume (P-V) analysis. PhyH and PaH were induced in rats by swim training and by abdominal aortic banding, respectively. Morphology of the heart was investigated by echocardiography. Characterization of cardiac function was completed by LV P-V analysis. In addition, histological and molecular biological measurements were performed. Echocardiography revealed myocardial hypertrophy of similar degree in both models, which was confirmed by post-mortem heart weight data. In aortic-banded rats we detected subendocardial fibrosis. Reactivation of fetal gene program could be observed only in the PaH model. PhyH was associated with increased stroke volume, whereas unaltered stroke volume was detected in PaH along with markedly elevated end-systolic pressure values. Sensitive indexes of LV contractility were increased in both models, in parallel with the degree of hypertrophy. Active relaxation was ameliorated in athlete's heart, whereas it showed marked impairment in PaH. Mechanical efficiency and ventriculo-arterial coupling were improved in PhyH, whereas they remained unchanged in PaH. Myocardial gene expression of mitochondrial regulators showed marked differences between PaH and PhyH. We provided the first comparative hemodynamic characterization of PhyH and PaH in relevant rodent models. Increased LV contractility could be observed in both types of LV hypertrophy; characteristic distinction was detected in diastolic function (active relaxation) and mechanoenergetics (mechanical efficiency), which might be explained by mitochondrial differences.