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Biomedical subjects

D G Gibson

Publications and source records attributed to D G Gibson.

At least 37 records · Page 2Linked to original sources
PubMed1999

The relationship of myocardial stroke work to coronary flow velocity immediately after aortic valve replacement.

BACKGROUND: The interrelations between myocardial stroke work and coronary flow velocity have not been fully defined during aortic valve replacement or with different cardioplegias. METHODS: Twenty-six patients (15 men age 63+/-13 years) who had elective isolated aortic valve replacement were studied by transesophageal Doppler echocardiography with simultaneous high fidelity left ventricular pressure. Fifteen patients received cold blood cardioplegia and 11 had warm blood cardioplegia. Myocardial stroke work and flow velocities in proximal left anterior descending coronary artery were quantified simultaneously before cardiopulmonary bypass and at 1, 6, 12, and 20 hours afterwards. RESULTS: Myocardial stroke work decreased postoperatively in both groups (160+/-19 versus 228+/-19 mJ/cm3 per minute, with cold blood cardioplegia; 135+/-22 versus 227+/-22 mJ/cm3 per minute with warm blood cardioplegia; both p<0.001 versus time, but p>0.05 versus cardioplegia, by two-way analysis of variance). Left anterior descending artery flow velocity-time integral per minute increased significantly in both groups (26.1+/-2.1 versus 15.0+/-2.1 m/min with cold blood cardioplegia; 32.8+/-2.5 versus 14.4+/-2.5 m/min with warm blood cardioplegia; both p<0.001 versus time, but p>0.05 versus cardioplegia). Thus, at 1 hour postoperatively the mJ x cm(-3) x m(-1) x min ratio of myocardial stroke work to left anterior descending artery flow velocity-time integral decreased significantly in both groups (4.3+/-1.6 versus 16.3+/-1.7 mJ x cm(-3) x m(-1) x min with warm blood cardioplegia, and 7.4+/-1.4 versus 17.9+/-1.4 J x cm(-3) x m(-1) x min with cold blood cardioplegia; both p<0.001 versus time). Warm blood cardioplegia was also associated with a lower mean ratio perioperatively than that with cold blood cardioplegia (7.8+/-0.9 versus 10.9+/-0.7 mJ x cm(-3) x m(-1) x min, p = 0.014). CONCLUSIONS: Coronary hyperemia occurs for at least 20 hours postoperatively when myocardial stoke work has decreased. The ratio of myocardial stroke work to coronary flow velocity appears to be more sensitive than either alone in differentiating the effect of warm versus cold blood cardioplegia.

Aortic Valve↗
PubMed1999

Electromechanical left ventricular behavior after nonsurgical septal reduction in patients with hypertrophic obstructive cardiomyopathy.

OBJECTIVES: To investigate the electromechanical consequences of nonsurgical septal reduction in a group of patients with hypertrophic obstructive cardiomyopathy (HOCM). BACKGROUND: Patients with HOCM may benefit symptomatically from nonsurgical septal reduction as an alternative to dual chamber pacing and sensing (DDD) pacing and surgical myectomy. METHODS: We studied 20 symptomatic patients with HOCM (12 men), mean age 52 +/- 17 years, before and after septal reduction using echocardiography and electrocardiogram (ECG). RESULTS: Septal reduction with a significant rise in cardiac enzymes was successfully achieved in all patients resulting in a 50% reduction in resting left ventricular (LV) outflow tract gradient within 24 h of procedure and an 80% reduction after six months. Left ventricular outflow tract diameter increased at 24 h with a further increase six months later. QRS duration increased by 35 ms at 24 h after procedure associated with right bundle branch block (RBBB) and significant rightward axis rotation in 16 patients. R-wave amplitude in V1 fell by 7 +/- 4 mm in 15/20 patients, 13 of whom developed reduction of septal long axis excursion. Left-axis deviation appeared in three patients and septal q-wave was suppressed in 12 long-axis excursion; peak shortening and lengthening rates all fell at the septal site by 20% at 24 h. Only septal excursion returned back to baseline values at six months. Wall motion also became incoordinate so that postejection septal shortening increased by three times control values at 24 h and by four times six months later. CONCLUSIONS: Nonsurgical septal reduction is associated with a drop in LV outflow tract obstruction and the creation of a localized myocardial infarction (MI) increasing LV outflow tract diameter. The technique also results in a consistent alteration of septal activation and secondary incoordination. The latter could play a significant role in gradient reduction and symptomatic improvement in a manner similar to that seen with DDD pacing.

Adult↗
PubMed1999

The effects of cardioplegia on coronary pressure-flow velocity relationships during aortic valve replacement.

OBJECTIVE: The acute physiological response of the coronary circulation to aortic valve replacement (AVR) has not been fully elucidated. This study aimed to characterize the changes in coronary perfusion pressure-flow velocity relationships, and to test whether this relationship is affected by cardioplegic method. METHODS: Nineteen patients (mean age 67 +/- 12 (SD) years, 9 males) undergoing aortic valve replacement who received either cold blood cardioplegia (CBC, n = 9) or warm blood cardioplegia (WBC, n = 10), were prospectively studied before and 30 min after the operation, using transesophageal Doppler echocardiography combined with high fidelity left ventricular (LV) and aortic pressures. We thus determined: (1) Diastolic flow velocities in proximal anterior descending coronary artery (LAD), and simultaneous aorta to LV pressure differences. (2) The slope (LAD proximal linear resistance) and pressure intercept (zero flow pressure) of this relationship. (3) Overall LAD linear resistance as the ratio of mean diastolic flow velocity to mean pressure difference between aorta and left ventricle. (4) LV myocardial stroke work. RESULTS: Following operation, myocardial stroke work fell from 5.2 +/- 2.7 to 3.0 +/- 1.7, mJ cm(-3) (P = 0.001), LAD mean diastolic flow velocity increased from 47 +/- 19 to 74 +/- 21, cm s(-1) (P = 0.0002). LAD overall linear resistance fell (0.75 +/- 0.24 vs. 1.26 +/- 0.26, mmHg cm(-1) s, P = 0.001). LAD proximal linear resistance, however, remained unchanged (P = 0.21), but the zero flow pressure fell (18 +/- 12.6 vs. 27 +/- 12.2, mmHg above LV end diastolic pressure, P = 0.013). With similar fall in myocardial work postoperatively, there was a greater fall in zero flow pressure after WBC than CBC (48 +/- 28 vs. 19 +/- 13,% of pre-op, P = 0.012), and a greater increase in flow velocity time integral (127 +/- 81 vs. 53 +/- 59,%, P = 0.039). CONCLUSION: Instantaneous diastolic LAD pressure-flow velocity relations in the early postoperative period can be explained more satisfactorily in terms of zero flow pressure and proximal linear resistance than simple resistance alone. The fall in zero flow pressure alone explains the increase in LAD flow velocity immediately after aortic valve replacement. The extent of this fall is greater after warm rather than cold blood cardioplegia.

Aged↗
PubMed1999

Effect of coronary occlusion on left ventricular function with and without collateral supply during beating heart coronary artery surgery.

OBJECTIVE: To study the effects of coronary occlusion and collateral supply on left ventricular (LV) function during beating heart coronary artery surgery. DESIGN: Prospective intraoperative study, performed at baseline, during wall stabilisation, coronary artery occlusion, and 2 and 10 minutes after reperfusion. Transoesophageal M mode echocardiograms, simultaneous high fidelity LV pressure, and thermodilution cardiac output were measured. LV anterior wall thickening, thinning velocities, thickening fraction, regional work, and power production were derived. Asynchrony during the isovolumic periods was quantified as cycle efficiency. SETTING: Tertiary referral cardiac centre. PATIENTS: 14 patients with stable angina, mean (SD) age 62 (7) years, undergoing left anterior descending artery grafting using the "Octopus" device. RESULTS: Collaterals were absent in nine patients and present in five. Epicardial stabilisation did not affect LV function. Results are expressed as mean (SD). Coronary occlusion (15.6 (2) minutes) depressed anterior wall thickening (1.4 (0.6) v 2.6 (0.6) cm/s) and thinning velocities (1.4 (0.5) v 3.0 (0.6) cm/s), regional work (2.2 (0.8) v 4.6 (0.6) mJ/cm2), and power (21 (4) v 33 (5) mW/cm2) in patients without collaterals (p < 0.05 for all), but only wall thinning (3.5 (0.5) v 4.8 (0.5) cm/s, p < 0.05) in patients with collaterals. All returned to baseline within 10 minutes of reperfusion. Cycle efficiency and regional work were impaired at baseline and fell during occlusion, regardless of collaterals. Within 10 minutes of reperfusion both had increased above baseline. CONCLUSIONS: Coronary occlusion for up to 15 minutes during beating heart coronary artery surgery depressed standard measurements of systolic and diastolic anterior wall function in patients without collaterals, but only those of diastolic function in patients with collaterals. Regional synchrony decreased in both groups. All disturbances regressed within 10 minutes of reperfusion.

Analysis of Variance↗
PubMed1999

Intraoperative cardiac troponin T release and lactate metabolism during coronary artery surgery: comparison of beating heart with conventional coronary artery surgery with cardiopulmonary bypass.

OBJECTIVE: To compare cardiac troponin T release and lactate metabolism in coronary sinus and arterial blood during uncomplicated coronary grafting on the beating heart with conventional coronary grafting using cardiopulmonary bypass. DESIGN: A prospective observational study with simultaneous sampling of coronary sinus and arterial blood: before and 1, 4, 10, and 20 minutes after reperfusion for analysis of cardiac troponin T and lactate. Cardiac troponin T was also analysed in venous samples taken 3, 6, 24, 48, and 72 hours after surgery. SETTING: Cardiac surgical unit in a tertiary referral centre. PATIENTS: 18 patients undergoing coronary grafting on the beating heart (10 single vessel and eight two-vessel grafting) and eight undergoing two-vessel grafting with cardiopulmonary bypass. RESULTS: Cardiac troponin T was detected in coronary sinus blood in all patients by 20 minutes after beating heart coronary artery surgery before arterial concentrations were consistently increased. Peak arterial and coronary sinus cardiac troponin T values on the beating heart during single (0.03 (0 to 0. 05) and 0.09 (0.07 to 0.16 microg/l, respectively) and two-vessel grafting (0.1 (0.07 to 0.11) and 0.19 (0.14 to 0.25) microg/l) were lower than the values obtained during cardiopulmonary bypass (0.64 (0.52 to 0.72) and 1.4 (0.9 to 2.0) microg/l) (p < 0.05). The area under the curve of venous cardiac troponin T over 72 hours for two-vessel grafting on the beating heart was less than with cardiopulmonary bypass (13 (10 to 16) v 68 (26 to 102) microg.h/l) (p < 0.001). Lactate extraction began within one minute of snare release during beating heart coronary surgery while lactate was still being produced 20 minutes after cross clamp release following cardiopulmonary bypass. CONCLUSIONS: Lower intraoperative and serial venous cardiac troponin T concentrations suggest a lesser degree of myocyte injury during beating heart coronary artery surgery than during cardiopulmonary bypass. Oxidative metabolism also recovers more rapidly with beating heart coronary artery surgery than with conventional coronary grafting. Coronary sinus cardiac troponin T concentrations increased earlier and were greater than arterial concentrations during beating heart surgery, suggesting that this may be a more sensitive method of intraoperative assessment of myocardial injury.

Aged↗
PubMed1999

Restrictive pericarditis.

BACKGROUND: Pericardial thickening is an uncommon complication of cardiac surgery. OBJECTIVES: To study pericardial thickening as the cause of severe postoperative venous congestion. SUBJECTS: Two men, one with severe aortic stenosis and single coronary artery disease, and one with coronary artery disease after an old inferior infarction. Both had coronary artery bypass grafting surgery. METHODS: Magnetic resonance imaging (MRI), Doppler echocardiography, and cardiac catheterisation. RESULTS: Venous pressure was raised in both patients. MRI showed mildly thickened pericardium, and cardiac catheterisation indicated diastolic equalization of pressures in the four chambers. Jugular venous pulse showed a dominant "Y" descent coinciding with early diastolic flow in the superior vena cava, and mitral and tricuspid Doppler forward flow proved restrictive physiology. The clinical background suggested pericardial disease so both patients had pericardiectomy. This proved the pericardium to be thickened; the extent of fibrosis also involved the epicardium. CONCLUSIONS: Although rare, restrictive pericarditis (restrictive ventricular physiology resulting from pericardial disease) should be considered to be a separate diagnostic entity because its pathological basis and treatment are different from intrinsic myocardial disease. This diagnosis may be confirmed by standard investigational techniques or may require diagnostic thoracotomy.

Aged↗
PubMed1998

Some factors that influence mechanical behavior of the left ventricle of the human heart in late systole: a feasibility study using finite element analysis.

In systole the left ventricle of the heart behaves mechanically in two modes simultaneously, passive and active. When in the former mode, the ventricle has to carry and react to the pressure increase within the cavity, while in the latter, force is generated within the myocardium itself through the contraction, i.e., active self-shortening, of the muscle fibers. When the deformations of these two opposing modes balance, isovolumic contraction occurs. After this phase, when the aortic valve has opened, the active mode dominates. Many models of the left ventricle under passive internal pressure have been reported, usually for analyzing the situation in diastole. Only a few attempts have been made to incorporate the self-activation effect present in systole. In this paper, a model for systole is described in which the active component has been treated by analogy to thermal stress analysis methods common in dealing with conventional engineering structures. The model was applied to the pressure and volume data for the ventricles of four patients with cardiac disease. A parametric study was then undertaken to investigate the influence of some of the mechanical factors on ventricular behavior. It was found that fiber angle has a very significant effect on the deformation of the ventricle and also that for ventricles with stiff myocardia, the passive component to the reaction of the ventricle was negligible.

Biomechanical Phenomena↗
PubMed1998

Angiotensin-converting enzyme (ACE) inhibitors revert abnormal right ventricular filling in patients with restrictive left ventricular disease.

OBJECTIVES: Our aim was to determine mechanisms underlying abnormalities of right ventricular (RV) diastolic function seen in heart failure. BACKGROUND: It is not clear whether these right-sided abnormalities are due to primary RV disease or are secondary to restrictive physiology on the left side of the heart. The latter regresses with angiotensin-converting enzyme inhibition (ACE-I). METHODS: Transthoracic echo-Doppler measurements of left- and right-ventricular function in 17 patients with systolic left ventricular (LV) disease and restrictive filling before and 3 weeks after the institution of ACE-I were compared with those in 21 controls. RESULTS: Before ACE-I, LV filling was restrictive, with isovolumic relaxation time short and transmitral E wave acceleration and deceleration rates increased (p < 0.001). Right ventricular long axis amplitude and rates of change were all reduced (p < 0.001), the onset of transtricuspid Doppler was delayed by 160 ms after the pulmonary second sound versus 40 ms in normals (p < 0.001) and overall RV filling time reduced to 59% of total diastole. Right ventricular relaxation was very incoordinate and peak E wave velocity was reduced. Peak RV to right atrial (RA) pressure drop, estimated from tricuspid regurgitation, was 45+/-6 mm Hg, and peak pulmonary stroke distance was 40% lower than normal (p < 0.001). With ACE-I, LV isovolumic relaxation time lengthened, E wave acceleration and deceleration rates decreased and RV to RA pressure drop fell to 30+/-5 mm Hg (p < 0.001) versus pre-ACE-I. Right ventricular long axis dynamics did not change, but tricuspid flow started 85 ms earlier to occupy 85% of total diastole; E wave amplitude increased but acceleration and deceleration rates were unaltered. Values of long axis systolic and diastolic measurements did not change. Peak pulmonary artery velocity increased (p < 0.01). CONCLUSIONS: Abnormalities of RV filling in patients with heart failure normalize with ACE-I as restrictive filling regresses on the left. This was not due to altered right ventricular relaxation or to a fall in pulmonary artery pressure or tricuspid pressure gradient, but appears to reflect direct ventricular interaction during early diastole.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Left ventricular long axis disturbances as predictors for thallium perfusion defects in patients with known peripheral vascular disease.

OBJECTIVE: To compare resting long axis echocardiography with adenosine thallium-201 emission tomography in detecting myocardial ischaemic abnormalities in patients before peripheral vascular surgery. DESIGN: A prospective and blinded preoperative examination of resting left ventricular minor and long axes and myocardial perfusion during adenosine vasodilatation using thallium-201 emission tomography. SETTING: A tertiary referral centre for cardiac and vascular disease equipped with invasive, non-invasive, and surgical facilities. SUBJECTS: 65 patients (40 men) with significant peripheral vascular disease, mean (SD) age 63 (10) years, and 21 control subjects of similar age. METHODS: Segments were classified as normal, with fixed or reversible defects according to thallium-201 myocardial perfusion tomography. Systolic long axis abnormalities were either reduced excursion and/or abnormal shortening after A2, and diastolic abnormalities either delayed onset of lengthening > 80 ms and/or reduced peak lengthening rate < 4.5 cm/s. Segmental perfusion defects were compared with the equivalent long axes; anteroseptal for septal, inferoseptal for posterior, and lateral for left side giving a total of 195 segments. RESULTS: Systolic long axis abnormalities predicted fixed thallium defects (sensitivity 86%, specificity 87%, positive predictive value 0.78, negative predictive value 0.93, p < 0.001), and diastolic abnormalities correlated with reversible perfusion defects (sensitivity 90%, specificity 85%, positive predictive value 0.72, negative predictive value 0.95, p < 0.001). Echocardiography characteristics of the true and false positive segments were not different in the site or the extent of abnormalities. CONCLUSION: Systolic long axis abnormalities predict fixed and diastolic reversible thallium perfusion defects in patients with peripheral vascular disease. Ventricular long axis may thus have a value as a screening test before peripheral vascular surgery as well as providing a means of monitoring myocardial perfusion. The high negative predictive values indicate that a negative long axis study makes significant perfusion abnormalities very unlikely in patients with high pretest probability of coronary artery disease.

Adenosine↗
PubMed1998

Abnormal ventricular activation and repolarisation during dobutamine stress echocardiography in coronary artery disease.

OBJECTIVE: To assess possible ECG changes caused by dobutamine stress and their relation to wall motion disturbances in patients with coronary artery disease. DESIGN: Prospective recording and analysis of 12 lead ECG at rest and during each stage of dobutamine stress echocardiography, and correlation with wall motion changes. SETTING: A tertiary referral centre for cardiac disease equipped with non-invasive facilities for pharmacological stress tests. SUBJECTS: 27 patients, mean (SD) age 60 (8) years, with documented evidence of coronary artery disease in whom dobutamine stress echo was clinically indicated, and 17 controls of similar age. RESULTS: In controls, all ECG intervals shortened with increasing heart rate but in the patient group only PR and QT intervals shortened while QRS duration broadened and QTc interval prolonged progressively. In the 27 patients, 16 developed chest pain, 15 with reduced left ventricular long axis systolic excursion (p < 0.001), and all showed reduced peak lengthening rate; ST segment shift appeared in 16, 13 of whom developed chest pain, but did not correlate with reduction of either systolic long axis excursion or peak lengthening rate; QRS duration broadened in 20, 16 with reduction of long axis excursion (p < 0.02) which was more often seen at the septum (p < 0.005); QTc interval prolonged in 19, all of whom had associated reduction of peak long axis lengthening rate (p < 0.02). CONCLUSIONS: QRS duration and QTc interval both normally shorten with dobutamine stress, while in coronary artery disease they both lengthen: changes in QRS duration correlate with systolic and QTc interval with diastolic left ventricular wall motion disturbances. ST segment shift also occurred in most patients, but without consistent correlation with wall motion abnormalities. It was thus less discriminating than the other two abnormalities in this respect.

Aged↗
PubMed1998

Intraoperative release of troponin T in coronary venous and arterial blood and its relation to recovery of left ventricular function and oxidative metabolism following coronary artery surgery.

OBJECTIVE: To investigate the intraoperative release of troponin T during uncomplicated coronary artery surgery and to determine its relation to ischaemic time and to recovery of left ventricular function and oxidative metabolism. DESIGN: A prospective observational study. SETTING: Cardiac surgical unit in a tertiary referral centre. METHODS: Troponin T, creatine kinase, and lactate were analysed from arterial and coronary sinus samples taken before operation, and 1, 4, 6, 10, 20, 35, and 45 minutes after cross clamp release. Net myocardial troponin T release and lactate extraction were derived from their respective arteriovenous differences. Haemodynamic measurements were made using a thermodilution pulmonary artery catheter. PATIENTS: 45 patients, mean (SD) age 62 (9) years, with two or three vessel coronary artery disease and chronic stable angina undergoing routine coronary artery surgery. RESULTS: Before operation, troponin T concentrations were not raised, but within one minute of cross clamp release they increased progressively in both coronary sinus and arterial blood for the entire 45 minutes of reperfusion studied. Coronary sinus troponin T concentrations were consistently higher than arterial concentrations at all time points (p < 0.001), indicating net troponin T release by the myocardium. Peak net troponin T release and area under the curve of net troponin T release correlated closely with ischaemic time (r = 0.58 and r = 0.61, p < 0.0001 for both). Area under the curve of arterial troponin T concentration was also significantly correlated with ischaemic time (r = 0.44, p < 0.01). Patients with cross clamp times longer than 72 minutes (upper quartile for ischaemic time) had greater troponin T release, delayed reversion to lactate extraction, and lower left ventricular stroke work index three hours after surgery, compared with patients who had short (< 50 minutes, lower quartile) and intermediate (51-71 minutes, interquartile) cross clamp times. Peak net troponin T release and area under the curve of arterial troponin T concentration were inversely correlated with left ventricular stroke work index three hours after surgery (r = -0.57, r = -0.38, p < 0.01). CONCLUSIONS: Troponin T concentrations increased in every patient after cross clamp release, and were consistently higher in coronary sinus blood than in arterial blood, indicating net myocardial release of troponin T during the period of reperfusion. Intraoperative net troponin T release has functional significance, as it is closely related to ischaemic time and reflects delayed recovery of left ventricular function and oxidative metabolism; therefore, its measurement may contribute to the perioperative assessment of myocardial injury sustained during coronary artery surgery.

Biomarkers↗
PubMed1998

Echo derived variables predicting exercise tolerance in patients with dilated and poorly functioning left ventricle.

OBJECTIVE: To determine whether resting echo derived measurements predict exercise tolerance and its interrelation with heart rate response and ventilation drive in patients with systolic left ventricular disease. DESIGN: Prospective echocardiographic examination followed by cardiopulmonary exercise testing. SETTING: A tertiary referral centre for cardiac diseases. SUBJECTS: 21 patients (11 with coronary artery disease, 10 with idiopathic dilated cardiomyopathy) with end diastolic dimension > 6.4 cm, shortening fraction < 25%, and in sinus rhythm. There were 11 age matched normal controls. RESULTS: In the patients, peak oxygen consumption (mVo2) correlated with right ventricular long axis excursion (r = 0.62); 65% of the variance in mVo2 was predictable using a multivariate model with right ventricular long axis excursion and peak lengthening rate, and peak mitral atrial filling velocity as independent variables. Aetiology was not an independent predictor, although the right ventricular long axis excursion (mean (SD)) was greater in patients with idiopathic dilated cardiomyopathy than in those with coronary artery disease (2.4 (0.5) cm v 1.6 (0.5) cm, p < 0.001). Peak heart rate correlated with duration of mitral regurgitation (r = -0.52) and the slope of ventilation against CO2 production correlated with M mode isovolumic relaxation time (r = 0.61). CONCLUSIONS: In patients with systolic left ventricular dysfunction, more than half the variance in exercise tolerance can be predicted by factors measured on echocardiography at rest, particularly right ventricular long axis excursion.

Cardiomyopathy, Dilated↗
PubMed1997

Reproducibility and reliability of middle cerebral artery occlusion using a silicone-coated suture (Koizumi) in rats.

The best technical approach to rat middle cerebral artery occlusion (MCAO) using a nylon-monofilament suture remains unsettled, regarding the usefulness of coated or uncoated sutures. Three investigators with different degrees of experience: A, well skilled; B, 2 years of experience; C, a novice with 6 months of experience, each subjected 10 Sprague-Dawley rats to permanent MCAO using low-viscosity silicone-coated sutures with a mean diameter 0.468+/-0.013 mm (mean+/-S.D.) at the tip and 0.361+/-0.013 mm in the body. Post-mortem corrected infarct size 24 h after MCAO was similar among the three investigators: A, 204.7+/-33.2 mm3; B, 212.6+/-42.8, and C, 195.9+/-44.4. The coefficient of variation was 16.2% to 22.7%, and 19.4% for the three investigators. This study suggests that experimental stroke with silicone-coated sutures (Koizumi's method) provides good reproducibility and reliability, among investigators of varying experience.

Animals↗
PubMed1997

Stress-induced left ventricular outflow tract obstruction: a potential cause of dyspnea in the elderly.

OBJECTIVES: We sought to identify the pattern of disturbed left ventricular physiology associated with symptom development in elderly patients with effort-induced breathlessness. BACKGROUND: Limitation of exercise tolerance by dyspnea is common in the elderly and has been ascribed to diastolic dysfunction when left ventricular cavity size and systolic function appear normal. METHODS: Dobutamine stress echocardiography was used in 30 patients (mean [+/-SD] age 70 +/- 12 years; 21 women, 9 men) with exertional dyspnea and negative exercise test results, and the values were compared with those in 15 control subjects. RESULTS: Before stress, left ventricular end-diastolic and end-systolic dimensions were reduced, fractional shortening was increased, and the basal septum was thickened (2.3 +/- 0.5 vs. 1.4 +/- 0.2 cm, p < 0.001, vs. control subjects) in the patients, but posterior wall thickness did not differ from that in control subjects. Left ventricular outflow tract diameter, measured as systolic mitral leaflet septal distance, was significantly reduced (13 +/- 4.5 vs. 18 +/- 2 mm, p < 0.001). Isovolumetric relaxation time was prolonged, and peak left ventricular minor axis lengthening rate was reduced (8.1 +/- 3.5 vs. 10.4 +/- 2.6 cm/s, p < 0.05), suggesting diastolic dysfunction. Transmitral velocities and the E/A ratio did not differ significantly. At peak stress, heart rate increased from 66 +/- 8 to 115 +/- 20 beats/min in the control subjects, but blood pressure did not change. Transmitral A wave velocity increased, but the E/A ratio did not change. Left ventricular outflow tract velocity increased from 0.8 +/- 0.1 to 2.0 +/- 0.2 m/s, and mitral leaflet septal distance decreased from 18 +/- 2 to 14 +/- 3 mm, p < 0.001. In the patients, heart rate rose from 80 +/- 12 to 132 +/- 26 beats/min and systolic blood pressure from 143 +/- 22 to 170 +/- 14 mm Hg (p < 0.001 for each), but left ventricular dimensions did not change. Peak left ventricular outflow tract velocity increased from 1.5 +/- 0.5 m/s (at rest) to 4.2 +/- 1.2 m/s; mitral leaflet septal distance fell from 13 +/- 4.5 to 2.2 +/- 1.9 mm (p < 0.001); and systolic anterior motion of mitral valve appeared in 24 patients (80%) but in none of the control subjects (p < 0.001). Measurements of diastolic function did not change. All patients developed dyspnea at peak stress, but none developed a new wall motion abnormality or mitral regurgitation. CONCLUSIONS: Although our patients fulfilled the criteria for "diastolic heart failure," diastolic dysfunction was not aggravated by pharmacologic stress. Instead, high velocities appeared in the left ventricular outflow tract and were associated with basal septal hypertrophy and systolic anterior motion of the mitral valve. Their appearance correlated closely with the development of symptoms, suggesting a potential causative link.

Aged↗