Papers by Andrew Macisaac
Pulmonary Circulation, 2015
Left ventricular diastolic dysfunction is a well-described complication of systemic hypertension.... more Left ventricular diastolic dysfunction is a well-described complication of systemic hypertension. However, less is known regarding the effect of chronic pressure overload on right ventricular (RV) diastolic function. We hypothesized that pulmonary hypertension (PHT) is associated with abnormal RV early relaxation and that this would be best shown by invasive pressure measurement. Twenty-five patients undergoing right heart catheterization for investigation of breathlessness and/or suspected PHT were studied. In addition to standard measurements, RV pressure was sampled with a high-fidelity micromanometer, and RV pressure/time curves were analyzed. Patients were divided into a PHT group and a non-PHT group on the basis of a derived mean pulmonary artery systolic pressure of 25 mmHg. Eleven patients were classified to the PHT group. This group had significantly higher RV minimum diastolic pressure ([Formula: see text] vs. [Formula: see text] mmHg, [Formula: see text]) and RV end-diastolic pressure (RVEDP; [Formula: see text] vs. [Formula: see text] mmHg, [Formula: see text]), and RV τ was significantly prolonged ([Formula: see text] vs. [Formula: see text] ms, [Formula: see text]). There were strong correlations between RV τ and RV minimum diastolic pressure ([Formula: see text], [Formula: see text]) and between RV τ and RVEDP ([Formula: see text], [Formula: see text]). There was a trend toward increased RV contractility (end-systolic elastance) in the PHT group ([Formula: see text] vs. [Formula: see text] mmHg/mL, [Formula: see text]) and a correlation between RV systolic pressure and first derivative of maximum pressure change ([Formula: see text], [Formula: see text]). Stroke volumes were similar. Invasive measures of RV early relaxation are abnormal in patients with PHT, whereas measured contractility is static or increasing, which suggests that diastolic dysfunction may precede systolic dysfunction. Furthermore, there is a strong association between measures of RV relaxation and RV filling pressures.
Global Heart, 2014
Conclusion: Adult patients with ASD have an increased mortality compared to healthy controls. The... more Conclusion: Adult patients with ASD have an increased mortality compared to healthy controls. The risk does not change with age at operation. Those without closure of an ASD have a significantly higher mortality compared to those with closure. Even adult patients with ASDs that are considered hemodynamically un-important seem to carry an increased mortality risk.
Southern Medical Journal, 2006
Background: The discordant relationship between fractional low reserve (FFR) and coronary low res... more Background: The discordant relationship between fractional low reserve (FFR) and coronary low reserve (CFR) is incompletely understood. We performed a study to assess the contributions of microcirculatory disease and residual epicardial disease to this relationship. methods: Consecutive patients undergoing PCI for stable angina and stabilized NSTEMI with single vessel disease were included in the study. FFR, index of microcirculatory resistance (IMR) and CFR were measured using a pressure wire pre and post PCI. A CFR value ≤2.0 and an FFR ≤0.8 were used as thresholds for ischaemia.
Australian and New Zealand Journal of Medicine, 1992
European journal of echocardiography : the journal of the Working Group on Echocardiography of the European Society of Cardiology, 2010
Left ventricular (LV) strain and strain rate have been proposed as novel indices of systolic func... more Left ventricular (LV) strain and strain rate have been proposed as novel indices of systolic function; however, there are limited data about the effect of acute changes on these parameters. Simultaneous Millar micromanometer LV pressure and echocardiographic assessment were performed on 18 patients. Loading was altered sequentially by the administration of glyceryl trinitrate (GTN) and saline fluid loading. Echocardiographic speckle tracking imaging was used to quantify the peak systolic strain (S) and peak systolic strain rate (SR S) and dp/dt max was recorded from the micromanometer data. GTN administration decreased preload (LV end diastolic pressure [LVEDP]: 15.7 vs. 8.4 mmHg, P < 0.001) and afterload (end systolic wall stress: 74 vs. 43 x 10(3)dyn/cm(2), P < 0.001). Administration of fluid increased preload (LVEDP: 11.3 vs. 18.1 mmHg, P < 0.001) and increased wall stress (53 vs. 62 x 10(3)dyn/cm(2), P < 0.003). Administration of GTN resulted in increased circumferen...
Heart Lung and Circulation, 2008
Heart, lung & circulation, 2014
A 34 year-old male presented with exertional dyspnoea. He had a past history of mechanical mitral... more A 34 year-old male presented with exertional dyspnoea. He had a past history of mechanical mitral (Carbomedics 29 mm) and aortic valve (Carbomedics 23 mm) replacements for rheumatic heart disease at the age of 19. Cardiovascular examination demonstrated dual mechanical heart sounds with a systolic murmur. Fluoroscopy revealed a radio-opaque ring within the mitral valve prosthesis orifice ( : arrows in Panel A; Video 1). Transthoracic echocardiography confirmed raised mean valve gradients (mitral valve: 11 mmHg, aortic valve: 43 mmHg). Transoesophageal echocardiography demonstrated intermittent failure of one of the mitral leaflets to open (Video 2). At cardiac surgery, calcified pannus was found to be infiltrating the mechanic mitral valve orifice. The margin of the pannus corresponded to the fluoroscopic ring ( : arrows in Panel B point to pannus on the ventricular surface of the mechanical mitral valve). Such a fluoroscopic ring of pannus is not seen with normal mechanical valve prostheses ( : arrows in Panel C point to normal leaflets of an appropriately functioning mechanical aortic valve prosthesis. Note that a fluoroscopic ring of pannus is not observed infiltrating the prosthesis). Both valve prostheses were replaced (27/29 mm On-X bileaflet mechanical prosthesis in the mitral position, 23 mm On-X mechanical prosthesis in the aortic position). The patient has remained well after his second valve replacement operations. Fluoroscopic detection of a calcified ring within a prosthetic valve orifice may be a useful novel sign of calcified pannus infiltration that may complicate prosthetic valve function.
Journal of Organ Dysfunction, 2009
Heart disease is a leading cause of global morbidity and mortality. Cardiovascular disease, most ... more Heart disease is a leading cause of global morbidity and mortality. Cardiovascular disease, most of which occurs secondary to atherosclerosis, accounted for more than one-third of all deaths in Australia in 2006, and this is likely to increase as the population ages and the ...
Circulation. Cardiovascular interventions, 2012
The relationship between epicardial stenosis and microvascular resistance remains controversial. ... more The relationship between epicardial stenosis and microvascular resistance remains controversial. Exploring the relationship is critical, as many tools used in interventional cardiology imply minimal and constant resistance. However, variable collateralization may impact well on these measures. We hypothesized that when collateral supply was accounted for, microvascular resistance would be independent of epicardial stenosis. Forty patients with stable angina were studied before and following percutaneous intervention. A temperature and pressure sensing guide wire was used to derive microvascular resistance using the index of microcirculatory resistance (IMR), defined as the hyperemic distal pressure multiplied by the hyperemic mean transit time. Lesion severity was assessed using fractional flow reserve. For comparison, evaluation of an angiographically normal reference vessel from the same subject also was undertaken. Both simple IMR (sIMR) and IMR corrected for collateral flow (cIM...
Heart Lung and Circulation, 2008
Circulation. Cardiovascular interventions, 2013
The use of fractional flow reserve in patients with non-ST-segment-elevation myocardial infarctio... more The use of fractional flow reserve in patients with non-ST-segment-elevation myocardial infarction (NSTEMI) is a controversial issue. We undertook a study to assess the vasodilatory capacity of the coronary microcirculation in patients with NSTEMI when compared with a model of preserved microcirculation (stable angina [SA] cohort: culprit and nonculprit vessel) and acute microcirculatory dysfunction (ST-segment-elevation myocardial infarction [STEMI] cohort). We hypothesized that the vasodilatory response of the microcirculation would be preserved in NSTEMI. A total of 140 patients undergoing single vessel percutaneous coronary intervention were included: 50 stable angina, 50 NSTEMI, and 40 STEMI. The index of microvascular resistance (IMR), fractional flow reserve, and coronary flow reserve were measured before stenting in the culprit vessel and in an angiographically normal nonculprit vessel in patients with SA. The resistive reserve ratio, a measure of the vasodilatory capacity o...
Journal of the American Society of Echocardiography, 2008
Background: Left ventricular torsion, resulting from the rotation of the base and apex of the ven... more Background: Left ventricular torsion, resulting from the rotation of the base and apex of the ventricle in opposite directions, may be an important component of normal cardiac function both at rest and with exercise. The effect of exercise on torsion in the general population and the influence of aging on changes in torsion with exercise are not known.
Journal of the American Society of Echocardiography, 2005
Abnormal motion of the interventricular septum (ASM), seen post cardiac operation, with left bund... more Abnormal motion of the interventricular septum (ASM), seen post cardiac operation, with left bundle branch block or right ventricular pacing, may affect septal mitral annular motion and correlation of the ratio between the velocity of early diastolic mitral inflow and the early diastolic mitral annular velocity (E/Ea) with pulmonary capillary wedge pressure (PCWP). We examined the effect of ASM on the relationship between E/Ea and E/Vp (propagation velocity of mitral inflow) ratios and PCWP in adult patients in the intensive care unit (14 with normal septal motion [NSM], 36 with ASM) undergoing echocardiography and pulmonary artery catheterization. E/Ea correlated well with PCWP during NSM ( r = 0.86 lateral annulus, r = 0.75 septal annulus), but poorly during ASM ( r = 0.36 lateral annulus, r = 0.39 septal annulus). E/Vp correlated poorly with PCWP ( r = 0.05 NSM, r = 0.17 ASM). For patients who are critically ill, E/Vp ratios poorly estimate PCWP. During NSM, E/Ea ratios measured at the lateral or septal annulus correlate well with PCWP. ASM affects E/Ea ratios at both the septal and lateral annulus, making E/Ea ratios unreliable for estimating PCWP in this group.
Journal of the American College of Cardiology, 1994
The purpose of this study was to determine the incidence and clinical characteristics of pulmonar... more The purpose of this study was to determine the incidence and clinical characteristics of pulmonary hemorrhage after intracoronary stent placement. Patients undergoing intracoronary stent placement receive intense anticoagulation to prevent stent thrombosis. Pulmonary hemorrhage during intense anticoagulation is uncommon in other clinical settings but has been diagnosed at our institution after stent placement. The clinical records of 88 consecutive patients undergoing intracoronary stent placement at a single tertiary referral center were reviewed for evidence of pulmonary hemorrhage. The diagnosis of pulmonary hemorrhage required bronchoscopic demonstration of fresh blood or thrombus in the airways of patients with sudden onset of hemoptysis, dyspnea or hypoxemia and new pulmonary infiltrates on chest radiograph. Pulmonary hemorrhage was identified in 4 (4.5%) of 88 patients undergoing intracoronary stent placement. Patients commonly presented with dyspnea, hemoptysis, hypoxemia, new pulmonary infiltrates on chest radiograph and excessive prolongation of the activated partial thromboplastin time. Mean onset of symptoms was 31.5 h after the procedure. Three of four patients were treated for presumed cardiogenic pulmonary edema until invasive hemodynamic monitoring revealed normal left ventricular filling pressures. Pulmonary hemorrhage resulted in prolonged admissions in the intensive care unit and hospital. One patient died. Pulmonary hemorrhage after coronary stent placement was commonly misdiagnosed and was associated with significant morbidity and mortality in our patients. Although its mechanism is unclear, excessive anticoagulation was a likely contributing factor. Clinical trials comparing varying strategies and intensities of anticoagulation may be indicated.
Journal of the American College of Cardiology, 1993
The treatment of coronary atherosclerosis requires an understanding of the pathophysiology of pla... more The treatment of coronary atherosclerosis requires an understanding of the pathophysiology of plaque rupture. The rupture of lipid-laden, macrophage-rich plaques initiates unstable angina, acute myocardial infarction and sudden cardiac death. Plaque rupture occurs when the circumferential tension on a plaque exceeds its tensile strength, an event that cannot be predicted by coronary angiography. The incidence of plaque rupture appears to be reduced in patients receiving cholesterol-lowering therapy, beta-adrenergic blocking agents and, possibly, angiotensin-converting enzyme inhibitors and antioxidants. Not all ruptured coronary plaques produce an acute coronary syndrome. The consequences of plaque rupture depend on the extent of thrombus formation over the fissured plaque. This is determined by flow characteristics within the vessel as well as the activity of the thrombotic and fibrinolytic systems. Recent advances in cardiovascular molecular biology, coronary diagnostic techniques and cardiac therapeutics have opened windows of opportunity to study and modify the factors leading to plaque rupture. The local modification of gene expression to alter plaque composition and to elucidate and subsequently inhibit the prothrombotic and fibrinolytic defects that promote coronary thrombosis may, in future, prevent plaque rupture and its consequences. The application of such a concerted interdisciplinary approach promises a paradigm shift in the management of coronary artery disease toward the prevention of plaque rupture and its sequelae.
Journal of the American College of Cardiology, 1995
Objectives. This study sought to determine the success and complication rates of high speed rotat... more Objectives. This study sought to determine the success and complication rates of high speed rotational coronary atherectomy in calcified and noncalcified lesions.
Journal of Applied Physiology, 2010
La Gerche A, MacIsaac AI, Burns AT, Mooney DJ, Inder WJ, Voigt JU, Heidbuchel H, Prior DL. Pulmon... more La Gerche A, MacIsaac AI, Burns AT, Mooney DJ, Inder WJ, Voigt JU, Heidbuchel H, Prior DL. Pulmonary transit of agitated contrast is associated with enhanced pulmonary vascular reserve and right ventricular function during exercise. Pulmonary transit of agitated contrast (PTAC) occurs to variable extents during exercise. We tested the hypothesis that the onset of PTAC signifies flow through larger-caliber vessels, resulting in improved pulmonary vascular reserve during exercise. Forty athletes and fifteen nonathletes performed maximal exercise with continuous echocardiographic Doppler measures [cardiac output (CO), pulmonary artery systolic pressure (PASP), and myocardial velocities] and invasive blood pressure (BP). Arterial gases and B-type natriuretic peptide (BNP) were measured at baseline and peak exercise. Pulmonary vascular resistance (PVR) was determined as the regression of PASP/CO and was compared according to athletic and PTAC status. At peak exercise, athletes had greater CO (16.0 Ϯ 2.9 vs. 12.4 Ϯ 3.2 l/min, P Ͻ 0.001) and higher PASP (60.8 Ϯ 12.6 vs. 47.0 Ϯ 6.5 mmHg, P Ͻ 0.001), but PVR was similar to nonathletes (P ϭ 0.71). High PTAC (defined by contrast filling of the left ventricle) occurred in a similar proportion of athletes and nonathletes (18/40 vs. 10/15, P ϭ 0.35) and was associated with higher peak-exercise CO (16.1 Ϯ 3.4 vs. 13.9 Ϯ 2.9 l/min, P ϭ 0.010), lower PASP (52.3 Ϯ 9.8 vs. 62.6 Ϯ 13.7 mmHg, P ϭ 0.003), and 37% lower PVR (P Ͻ 0.0001) relative to low PTAC. Right ventricular (RV) myocardial velocities increased more and BNP increased less in high vs. low PTAC subjects. On multivariate analysis, maximal oxygen consumption (V O2max) (P ϭ 0.009) and maximal exercise output (P ϭ 0.049) were greater in high PTAC subjects. An exercise-induced decrease in arterial oxygen saturation (98.0 Ϯ 0.4 vs. 96.7 Ϯ 1.4%, P Ͻ 0.0001) was not influenced by PTAC status (P ϭ 0.96). Increased PTAC during exercise is a marker of pulmonary vascular reserve reflected by greater flow, reduced PVR, and enhanced RV function. right ventricle; pulmonary circulation; pulmonary vascular resistance; contrast echocardiography; athlete on November 22, 2010 jap.physiology.org Downloaded from
JACC: Cardiovascular Interventions, 2013
This study sought to investigate a novel method to calculate the index of microcirculatory resist... more This study sought to investigate a novel method to calculate the index of microcirculatory resistance (IMR) in the presence of significant epicardial stenosis without the need for balloon dilation to measure the coronary wedge pressure (P(w)). The IMR provides a quantitative measure of coronary microvasculature status. However, in the presence of significant epicardial stenosis, IMR calculation requires incorporation of the coronary fractional flow reserve (FFR(cor)), which requires balloon dilation within the coronary artery for P(w) measurement. A method to calculate IMR by estimating FFR(cor) from myocardial FFR (FFR(myo)), which does not require P(w) measurement, was developed from a derivation cohort of 50 patients from a single institution. This method to calculate IMR was then validated in a cohort of 72 patients from 2 other different institutions. Physiology measurements were obtained with a pressure-temperature sensor wire before coronary intervention in both cohorts. From the derivation cohort, a strong linear relationship was found between FFR(cor) and FFR(myo) (FFR(cor) = 1.34 × FFR(myo) - 0.32, r(2) = 0.87, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) by regression analysis. With this equation to estimate FFR(cor) in the validation cohort, there was no significant difference between IMR calculated from estimated FFR(cor) and measured FFR(cor) (21.2 ± 12.9 U vs. 20.4 ± 13.6 U, p = 0.161). There was good correlation (r = 0.93, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) and agreement by Bland-Altman analysis between calculated and measured IMR. The FFR(cor), and, by extension, microcirculatory resistance can be derived without the need for P(w). This method enables assessment of coronary microcirculatory status before or without balloon inflation, in the presence of epicardial stenosis.
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Papers by Andrew Macisaac