Abnormal coronary flow dynamics at rest and during tachycardia associated with impaired left ventricular relaxation in humans: implication for tachycardia-induced myocardial ischemia

Untangling the pathophysiologic link between coronary microvascular dysfunction and heart failure with preserved ejection fraction

Coronary microvascular disease (CMD), characterized by impaired coronary flow reserve (CFR), is a common finding in patients with stable angina. Impaired CFR, in the absence of obstructive coronary artery disease, is also present in up to 75% of patients with heart failure with preserved ejection fraction (HFpEF). Heart failure with preserved ejection fraction is a heterogeneous syndrome comprising distinct endotypes and it has been hypothesized that CMD lies at the centre of the pathogenesis of one such entity: the CMD–HFpEF endotype. This article provides a contemporary review of the pathophysiology underlying CMD, with a focus on the mechanistic link between CMD and HFpEF. We discuss the central role played by subendocardial ischaemia and impaired lusitropy in the development of CMD–HFpEF, as well as the clinical and research implications of the CMD–HFpEF mechanistic link. Future prospective follow-up studies detailing outcomes in patients with CMD and HFpEF are much needed to enhance our understanding of the pathological processes driving these conditions, which may lead to the development of physiology-stratified therapy to improve the quality of life and prognosis in these patients.

Risk factors and outcomes of myocardial injury after non-cardiac surgery in high-risk patients who underwent radical cystectomy

Radical cystectomy is considered the standard treatment for patients with muscle-invasive bladder tumors and has high postoperative complication rates among urological surgeries. High-risk patients, defined as those ≥45 years of age with history of coronary artery disease, stroke, or peripheral artery disease or those ≥65 years of age, can have a higher incidence of cardiac complications. Therefore, we evaluated the incidence, risk factors, and outcomes of myocardial injury after non-cardiac surgery (MINS) in high-risk patients who underwent radical cystectomy.This retrospective observational study analyzed 248 high-risk patients who underwent radical cystectomy. MINS was defined as serum troponin I concentration ≥0.04 mg/L within postoperative 3 days. The risk factors for MINS were evaluated by multivariate logistic regression analysis. Postoperative outcomes were evaluated. The 1-year survival after radical cystectomy was also compared between patients who developed MINS (MINS group) and those who did not (non-MINS group) by Kaplan-Meier analysis.MINS occurred in 35 patients (14.1%). Multivariate logistic regression analysis showed that early diastolic transmitral filling velocity (E)/early diastolic septal mitral annular velocity (E') ratio (odds ratio = 1.102, 95% confidence interval [1.009-1.203], P = .031) and large volume blood transfusion (odds ratio = 2.745, 95% confidence interval [1.131-6.664], P = .026) were significantly associated with MINS in high-risk patients who underwent radical cystectomy. Major adverse cardiac events and 1-year mortality were significantly higher in the MINS group than in the non-MINS group (17.1% vs 6.1%, P = .035; 28.6% vs 12.7%, P = .021, respectively). Kaplan-Meier analysis showed significantly lower 1-year survival in the MINS group than in the non-MINS group (P = .010).MINS occurred in 14.1% of patients. High E/E' ratio and large volume blood transfusion were risk factors for MINS in high-risk patients who underwent radical cystectomy. Postoperative major adverse cardiac events and 1-year mortality were significantly higher in the MINS group than in the non-MINS group. Preoperative evaluation of risk factors for MINS may provide useful information to detect cardiovascular complications after radical cystectomy in high-risk patients.

Risk factors of postoperative major adverse cardiac events after radical cystectomy: implication of diastolic dysfunction

Radical cystectomy, which is a standard treatment of muscle invasive and high-grade non-invasive bladder tumour, is accompanied with high rates of postoperative complications including major adverse cardiac events (MACE). Diastolic dysfunction is associated with postoperative complications. We evaluated perioperative risk factors including diastolic dysfunction related with MACE within 6 months after radical cystectomy. The 546 patients who underwent elective radical cystectomy were included. Diastolic dysfunction was defined as early transmitral flow velocity (E)/early diastolic mitral annulus velocity (e′) > 15. Logistic regression analysis, Kaplan-Meier survival analysis and log-rank test were performed. MACE within 6 months after radical cystectomy developed in 43 (7.9%) patients. MACE was related with female (odds ratio 2.546, 95% confidence interval 1.166–5.557, P = 0.019) and diastolic dysfunction (odds ratio 3.077, 95% confidence interval 1.147–8.252, P = 0.026). The 6-month mortality were significantly higher in the MACE group, and hospital stay and intensive care unit stay were significantly longer in the MACE group compared to the non-MACE group. Accordingly, preoperative diastolic dysfunction (E/e′ > 15) was related with postoperative MACE and MACE was related with 6-month survival after radical cystectomy. These results suggest that preoperative diastolic dysfunction can provide useful information on postoperative complications.

Coronary flow reserve/diastolic function relationship in angina-suffering patients with normal coronary angiography

AIMS

Coronary blood flow and diastolic function are well known to interfere with each other through mechanical and metabolic mechanisms. We aimed to assess the relationship between coronary flow reserve (CFR) and diastolic dysfunction in patients suffering from angina but with normal coronary angiography.

METHODS

In 16 patients with chest pain and angiographically normal coronary arteries, CFR was measured using transthoracic echo-Doppler by inducing hyperemia through dipyridamole infusion. Diastolic function (E/A, deceleration time, isovolumetric relaxation time [IVRT], propagation velocity [Vp]) and left ventricular mass were evaluated by means of two-dimensional transthoracic echocardiography.

RESULTS

The patients were initially divided into two groups on the grounds of CFR only (ACFR: altered CFR, n = 9; NACFR: unaltered CFR, n = 7). Thereafter they were divided into four groups on the grounds of CFR and diastolic function (NN: normal; AA: altered CFR/diastole; AN: altered CFR/normal diastole; NA: normal CFR/altered diastole). Most of the subjects were scheduled in AA (n = 8) or NA (n = 5) groups, which were taken into consideration for further analysis. Patients were not different regarding various risk factors. ACFR and AA patients were older with normal body weight in comparison with NACFR and NA patients (P < 0.05). In the AA group, CFR and diastolic variables were found to be related to each other.

CONCLUSION

Diastolic dysfunction and reduced CFR were correlated in patients with concomitant alterations of those variables only. Because most risk factors were shared with patients with altered diastolic properties only, our findings could represent a direct relationship between altered CFR and diastole.

NADH changes during hypoxia, ischemia, and increased work differ between isolated heart preparations

Langendorff-perfused hearts and working hearts are established isolated heart preparation techniques that are advantageous for studying cardiac physiology and function, especially when fluorescence imaging is a key component. However, oxygen and energy requirements vary widely between isolated heart preparations. When energy supply and demand are not in harmony, such as when oxygen is not adequately available, the imbalance is reflected in NADH fluctuations. As such, NADH imaging can provide insight into the metabolic state of tissue. Hearts from New Zealand white rabbits were prepared as mechanically silenced Langendorff-perfused hearts, Langendorff-perfused hearts, or biventricular working hearts and subjected to sudden changes in workload, instantaneous global ischemia, and gradual hypoxia while heart rate, aortic pressure, and epicardial NADH fluorescence were monitored. Fast pacing resulted in a dip in NADH upon initiation and a spike in NADH when pacing was terminated in biventricular working hearts only, with the magnitude of the changes greatest at the fastest pacing rate. Working hearts were also most susceptible to changes in oxygen supply; NADH was at half-maximum value when perfusate oxygen was at 67.8 ± 13.7%. Langendorff-perfused and mechanically arrested hearts were the least affected by low oxygen supply, with half-maximum NADH occurring at 42.5 ± 5.0% and 23.7 ± 4.6% perfusate oxygen, respectively. Although the biventricular working heart preparation can provide a useful representation of mechanical in vivo heart function, it is not without limitations. Understanding the limitations of isolated heart preparations is crucial when studying cardiac function in the context of energy supply and demand.

Prognostic value of left ventricular diastolic dysfunction in patients undergoing cardiac catheterization for coronary artery disease

We hypothesized that left ventricular (LV) diastolic dysfunction assessed by cardiac catheterization may be associated with increased risk for cardiovascular events. To test the hypothesis, we assessed diastolic function by cardiac catheterization (relaxation time constant (Tau) and end-diastolic pressure (EDP)) as well as Doppler echocardiography (early diastolic mitral annular velocity (e') and a ratio of early diastolic mitral inflow to annular velocities (E/e')) in 222 consecutive patients undergoing cardiac catheterization for coronary artery disease (CAD). During a followup of 1364 ± 628 days, 5 cardiac deaths and 20 unscheduled cardiovascular hospitalizations were observed. Among LV diastolic function indices, Tau > 48 ms and e' < 5.8 cm/s were each significantly associated with lower rate of survival free of cardiovascular hospitalization. Even after adjustment for potential confounders (traditional cardiovascular risk factors, the severity of CAD, and cardiovascular medications), the predictive value of Tau > 48 ms and e' < 5.8 cm/s remained significant. No predictive value was observed in EDP, E/e', or LV ejection fraction. In conclusion, LV diastolic dysfunction, particularly impaired LV relaxation assessed by both cardiac catheterization and Doppler echocardiography, is independently associated with increased risk for cardiac death or cardiovascular hospitalization in patients with known or suspected CAD.

Association of abnormal coronary microcirculatory function with impaired response of longitudinal left ventricular function during adenosine stress echocardiography in untreated hypertensive patients

AIMS

Coronary microcirculation is disturbed in hypertensive patients. We investigated the association of coronary flow reserve (CFR) with the response of left ventricular (LV) function as assessed by tissue Doppler imaging (TDI) during adenosine stress echocardiography in never-treated hypertensive patients.

METHODS AND RESULTS

We studied 90 hypertensive patients and 30 control subjects, matched for age and sex, by adenosine stress echocardiography. We measured: (i) CFR, E and A Doppler, S', E', A' mitral annulus velocities with TDI, as well as the E'/A' ratio and the E/E' ratio before and during adenosine infusion (ii) the %changes of the measured indices between baseline and adenosine infusion. After adenosine infusion, there was an increase in S', E', and A' in all patients and controls (P < 0.05). Compared with controls and patients with CFR ≥ 2.5, patients with CFR <2.5 showed a smaller increase in S' (28.6 vs. 30.0 vs. 11.1%, F for interaction = 14.592) and E' (33.3 vs. 33.3 vs.1.5%, F = 28.927) as well as a decrease in E'/A' (9.2 vs. 6.4% vs. -20.0%, F = 5.128) and an increase in E/E' (-6.1 vs. -1.6 vs. 30.5%. F = 12.780) after adenosine infusion (P < 0.05 for all comparisons). CFR was independently related to %changes of TDI parameters (regression coefficient b = 0.576 for S'; b = 0.517 for E'; b = 0.473 for E'/A'; b = -0.520 for E/E', respectively, P < 0.001). By the receiver operating curve, a CFR <2.5 predicted the median changes of all measured TDI markers, with a sensitivity and specificity over 70% (AUC >75%, P < 0.05).

CONCLUSION

An abnormal response of the LV longitudinal function during adenosine stress echocardiography is related to impaired CFR in untreated hypertensive patients.

Diagnosis and management of left ventricular diastolic dysfunction in the hypertensive patient

The progression of hypertensive involvement toward heart failure includes myocardial fibrosis and changes of left ventricular (LV) geometry. In the presence of these abnormalities, diastolic abnormalities occur and are defined as LV diastolic dysfunction (DD). They include alterations of both relaxation and filling, precede alterations of chamber systolic function and can induce symptoms of heart failure even when ejection fraction is normal. The prevalence of heart failure with normal ejection fraction (HFNEF) increased over time whereas the rate of death from this disorder remained unchanged. In this view, diagnosis, prognosis, and therapeutic management of DD and HFNEF in hypertensive patients is a growing public health problem. DD may be asymptomatic and identified occasionally during a Doppler-echocardiographic examination. This tool has gained, therefore, important clinical position for diagnosis of DD. Comprehensive assessment of diastolic function should be done not by a simple classification of DD progression but by estimating the degree of LV filling pressure (FP), a true determinant of symptoms and prognosis. This can be obtained by different ultrasound maneuvers/tools but the ratio between transmitral E velocity and pulsed tissue Doppler-derived early diastolic velocity (E/e' ratio) is the most feasible and accurate. The identification of left atrial enlargement may be useful in uncertain cases. The recommended management of DD in hypertensive patients should correspond to blood pressure (BP) lowering and to the attempt of reducing LV mass and normalizing LV geometry. Prospective studies with well-defined entry criteria are needed to establish whether this approach could reflect a better prognosis.

Nonacute coronary syndrome anginal chest pain

Anginal chest pain is one of the most common complaints in the outpatient setting. While much of the focus has been on identifying obstructive atherosclerotic coronary artery disease (CAD) as the cause of anginal chest pain, it is clear that microvascular coronary dysfunction (MCD) can also cause anginal chest pain as a manifestation of ischemic heart disease, and carries an increased cardiovascular risk. Epicardial coronary vasospasm, aortic stenosis, left ventricular hypertrophy, congenital coronary anomalies, mitral valve prolapse, and abnormal cardiac nociception can also present as angina of cardiac origin. For nonacute coronary syndrome (ACS) stable chest pain, exercise treadmill testing (ETT) remains the primary tool for diagnosis of ischemia and cardiac risk stratification; however, in certain subsets of patients, such as women, ETT has a lower sensitivity and specificity for identifying obstructive CAD. When combined with an imaging modality, such as nuclear perfusion or echocardiography testing, the sensitivity and specificity of stress testing for detection of obstructive CAD improves significantly. Advancements in stress cardiac magnetic resonance imaging enables detection of perfusion abnormalities in a specific coronary artery territory, as well as subendocardial ischemia associated with MCD. Coronary computed tomography angiography enables visual assessment of obstructive CAD, albeit with a higher radiation dose. Invasive coronary angiography remains the gold standard for diagnosis and treatment of obstructive lesions that cause medically refractory stable angina. Furthermore, in patients with normal coronary angiograms, the addition of coronary reactivity testing can help diagnose endothelial-dependent and -independent microvascular dysfunction. Lifestyle modification and pharmacologic intervention remains the cornerstone of therapy to reduce morbidity and mortality in patients with stable angina. This review focuses on the pathophysiology, diagnosis, and treatment of stable, non-ACS anginal chest pain.

Independent association of coronary flow reserve with left ventricular relaxation and filling pressure in arterial hypertension

BACKGROUND

It has been recognized that "cross-talk" occurs between coronary flow and left ventricular (LV) function. This study tested the hypothesis that impairment of coronary flow reserve (CFR) in arterial hypertension is associated with LV systolic and diastolic dysfunction, independent of abnormalities in LV geometry.

METHODS

We studied 59 newly diagnosed, never-treated hypertensive patients, using transthoracic Doppler echocardiography including pulsed Tissue Doppler of mitral annulus and CFR on left anterior descending artery (low-dose dipyridamole). The study population was divided into two groups on the basis of age-normalized relative wall thickness (RWTn): 36 patients with normal LV geometry (RWTn < or = 0.41) and 23 patients with LV concentric geometry (RWTn > 0.41).

RESULTS

Patients with LV concentric geometry (RWTn > 0.41) had significantly lower values of midwall shortening (but not of endocardial shortening), longer isovolumic relaxation time (IVRT), lower Tissue Doppler-derived early diastolic velocity (Em), higher ratio of transmitral E velocity to Em, and lower CFR as compared to patients with normal LV geometry (RWTn < or = 0.41). In the whole population, a lower CFR was significantly associated with lower values of midwall shortening and Em, longer IVRT, and higher E/Em ratio. After controlling for heart rate, mean blood pressure, and RWTn, only the relation of CFR with IVRT, Em, and E/Em ratio remained significant.

CONCLUSIONS

Reduced midwall mechanics is associated with lower CFR, a relationship that depends on LV concentric geometry. A reduced CFR is associated with both impaired relaxation and increased filling pressure, a relation that is independent of LV geometry and pressure load.

Incremental value of pulse wave velocity in the determination of coronary microcirculatory dysfunction in never-treated patients with essential hypertension

BACKGROUND

Coronary microcirculation is disturbed in essential hypertension. We investigated whether arterial stiffness determines coronary flow reserve (CFR) in hypertensive patients.

METHODS

We examined 100 never-treated hypertensives and 20 healthy controls. We measured (i) carotid-to-femoral pulse wave velocity (PWV); (ii) Systolic (V (s)) and diastolic (V (d)) coronary flow velocity, time integral (V (TI)-V (d)) of diastolic velocity and CFR after adenosine by transthoracic echocardiography; (iii) ratio of E wave from mitral inflow to Em of mitral annulus, as an index of left ventricular (LV) diastolic pressures using tissue Doppler; (iv) carotid intima-media thickness (IMT), as an index of vascular damage; and (v) 24-h blood pressure parameters using ambulatory blood pressure monitoring.

RESULTS

Patients had abnormal PWV, IMT, E/Em, resting V (d)/V (s), and CFR than controls (P < 0.05). In hypertensives, PWV was related to abnormal IMT and E/Em which in turn were related to reduced CFR (P < 0.05). PWV and E/Em were independent determinants of CFR and V (d)/V (s) (P < 0.05) in hypertensives. When added to a model including age, sex, smoking, LV mass (LVM), heart rate, 24-h systolic blood pressure (SBP), and E/Em, PWV had an incremental value in the determination of CFR (r (2) change from 0.25 to 0.46, P < 0.01). PWV >10.7 m/s predicted a CFR <2 with 79 and 75% and a CFR <2.6 with 83 and 82% sensitivity and specificity, respectively, using adjusted-receiver operating characteristic curve (ROC) analysis.

CONCLUSIONS

Elevated LV diastolic compressive forces on coronary microcirculation and the presence of generalized vascular damage may explain the association between PWV and CFR. PWV has an incremental value in the determination of impaired coronary microcirculation in hypertensive patients.

Coronary microvascular dysfunction after myocardial infarction: increased coronary zero flow pressure both in the infarcted and in the remote myocardium is mainly related to left ventricular filling pressure

OBJECTIVE

To investigate the underlying mechanisms of a decreased coronary flow reserve after myocardial infarction (MI) by analysing the characteristics of the diastolic hyperaemic coronary pressure-flow relationship.

DESIGN

Prospective study.

SETTING

Tertiary care hospital.

PATIENTS

68 patients with a recent MI and 27 patients with stable angina pectoris (AP; control group).

MAIN OUTCOME MEASURES

The intercept with the pressure axis (the zero flow pressure or Pzf) and slope index of the pressure-flow relationship (SIPF) were calculated from the simultaneously recorded hyperaemic intracoronary blood flow velocity and aortic pressure after successful coronary stenting.

RESULTS

A stepwise increase in Pzf from AP (14.6 (8.0) mm Hg), over non-Q-wave MI (22.5 (9.1) mm Hg), to Q-wave MI (37.1 (12.9) mm Hg; p<0.001) was observed. Similar changes in Pzf were found in a reference artery perfusing the non-infarcted myocardium. Multivariate analysis showed that in both regions the left ventricular end-diastolic pressure (LVEDP) was the most important determinant of the Pzf. The SIPF was not statistically different in the treated vessel between patients with MI and AP, but was increased in MI patients with a markedly increased LVEDP.

CONCLUSIONS

After an MI, the coronary pressure-flow relationship is shifted to the right both in the infarcted and in the non-infarcted remote myocardium, as shown by the increased Pzf. The correlation with Pzf suggests that elevated left ventricular filling pressures contribute to the impediment of myocardial perfusion in patients with infarction.

Diastolic dysfunction and diabetic cardiomyopathy: evaluation by Doppler echocardiography

Doppler echocardiography has largely contributed to show the existence of a distinct diabetic cardiomyopathy. Several studies have pointed out the evidence of left ventricular (LV) remodeling and hypertrophy in alterations of both midwall systolic mechanics and LV diastolic filling in diabetes mellitus (DM), independent of the coexistence of concomitant risk factors. Further progress will be provided by new ultrasound technologies in this clinical setting. The combination of pulsed tissue Doppler study of mitral annulus with transmitral inflow may be clinically valuable for obtaining information about left ventricular filling pressure (LVFP) and unmasking Doppler inflow pseudonormal pattern, a hinge point for the progression toward advanced heart failure. In the absence of epicardial coronary artery stenosis, the ultrasound assessment of coronary flow reserve (CFR) may identify the dysfunction of coronary microcirculation, in relation with glycemic levels, insulin resistance, sympathetic overdrive, endothelial dysfunction, abnormalities of the angiotensin-renin system, and LV remodeling/hypertrophy. Diastolic dysfunction and impairment of CFR may be associated in DM, with a likely common origin. In this view, a comprehensive transthoracic Doppler evaluation of diabetic patients should include the assessment of diastolic function and estimation of LVFP by tissue Doppler, and coronary microvascular function by CFR test. Additional analysis of regional wall motion during a stress test would be required in patients with suspected coronary artery disease, another cause of diastolic dysfunction.

Tachycardia-induced myocardial ischemia and diastolic dysfunction potentiate secretion of ANP, not BNP, in hypertrophic cardiomyopathy

The aim of this study was to investigate what factor determines tachycardia-induced secretion of atrial and brain natriuretic peptides (ANP and BNP, respectively) in patients with hypertrophic cardiomyopathy (HCM). HCM patients with normal left ventricular (LV) systolic function and intact coronary artery (n = 22) underwent rapid atrial pacing test. The cardiac secretion of ANP and BNP and the lactate extraction ratio (LER) were evaluated by using blood samples from the coronary sinus and aorta. LV end-diastolic pressure (LVEDP) and the time constant of LV relaxation of tau were measured by a catheter-tip transducer. These parameters were compared with normal controls (n = 8). HCM patients were divided into obstructive (HOCM) and nonobstructive (HNCM) groups. The cardiac secretion of ANP was significantly increased by rapid pacing in HOCM from 384 +/- 101 to 1,268 +/- 334 pg/ml (P < 0.05); however, it was not significant in control and HNCM groups. In contrast, the cardiac secretion of BNP was fairly constant and rather significantly decreased in HCM (P < 0.01). The cardiac ANP secretion was significantly correlated with changes in LER (r = -0.57, P < 0.01) and tau (r = 0.73, P < 0.001) in HCM patients. Tachycardia potentiates the cardiac secretion of ANP, not BNP, in patients with HCM, particularly when it induces myocardial ischemia and LV diastolic dysfunction.

Coronary flow reserve and myocardial diastolic dysfunction in arterial hypertension

The aim of this study was to assess the relation between coronary blood flow and left ventricular (LV) myocardial diastolic dysfunction in arterial hypertension. The study population included 30 hypertensive patients who were free of coronary artery disease and pharmacologic therapies. They underwent standard Doppler echocardiography and color tissue Doppler of the middle posterior septum at baseline and with high-dose dobutamine, and second-harmonic Doppler flow analysis of the distal left anterior descending coronary artery at baseline and after vasodilation by dipyridamole (0.56 mg/kg IV in 4'). Coronary flow reserve (CFR) was estimated as the ratio of hyperemic and baseline diastolic flow velocities. According to CFR, hypertensives were divided into 2 groups: 15 patients with normal CFR (>/=2) and 15 patients with reduced CFR (<2). The 2 groups were comparable for sex, age, body mass index, baseline heart rate, and blood pressure. LV mass index was greater in hypertensives with reduced CFR (p <0.01). By color tissue Doppler, baseline and high-dose dobutamine septal systolic velocities did not differ between the 2 groups. The ratio between myocardial velocities in early diastole and at atrial contraction (E(m)/A(m) ratio) was lower in patients with reduced CFR, both at baseline (p <0.05) and with high-dose dobutamine (p <0.00001). After adjusting for age, body mass index, LV mass index, and both high-dose dobutamine diastolic blood rate and heart rate by a multiple linear regression analysis, E(m)/A(m) ratio at high-dose dobutamine was independently associated with CFR in the overall population (beta 0.62, p <0.0005) (cumulative R(2) 0.38, p <0.0005). In conclusion, this study provides evidence of an independent association between CFR and myocardial diastolic function. In hypertensive patients without coronary artery stenosis, CFR alteration may be a determinant of myocardial diastolic dysfunction or diastolic impairment that should be taken into account as possibly contributing to coronary flow reduction.

Left ventricular hypertrophy in hypertension as a predictor of coronary events: relation to geometry

The present review examines epidemiological evidence for a relation of left ventricular hypertrophy with coronary heart disease, and mechanisms that may represent pathophysiological links between left ventricular hypertrophy and coronary events. Left ventricular hypertrophy has been demonstrated to be a powerful predictor of coronary heart disease, and when geometry is concentric the relation is even stronger. In addition to its association with risk factors for atherosclerosis and mechanisms that precipitate acute heart attacks, left ventricular hypertrophy also directly predisposes to and aggravates clinical presentation of coronary heart disease through a number of biological mechanisms. These include the following: increase in oxygen requirement related to left ventricular geometry; coronary hypertension, with endothelial dysfunction and reduced coronary reserve; diastolic dysfunction; and structural remodelling of myocardium and vascular bed. Some of these alterations are also worsened by underlying coronary heart disease, and can potentially be maintained by loop mechanisms. A recognizable stage of abnormal coronary haemodynamics in the context of left ventricular hypertrophy is probably that at which coronary reserve is impaired in the absence of any other sign of heart disease; in many circumstances, this may occur early in the disease process.

Abnormal coronary flow profiles at rest and during rapid atrial pacing in patients with hypertrophic cardiomyopathy

To examine the mechanism of myocardial ischemia in hypertrophic cardiomyopathy (HCM), coronary flow velocity was measured in the left anterior descending coronary artery (LAD) using a Doppler guide wire in 11 patients with HCM and in 8 normal controls. The average peak velocity (APV), percent increase of APV (%APV), and APV during systole (Vs) and diastole (Vd) were calculated at rest and during rapid atrial pacing. The APV in HCM reached a peak value at a heart rate of 90 beats/min, while in the controls the APV increased continuously until the heart rate reached 130 beats/min [%APV (130 beats/min); 103+/-30% in HCM vs 139+/-23% in controls, p<0.04]. During rapid atrial pacing, Vs in the controls increased, whereas Vs in HCM decreased further. During high-rate pacing, Vd in HCM reached a peak value at a heart rate of 90 beats/min, whereas in the controls, Vd increased continuously until the heart rate reached 130 beats/min. The acceleration rate of early diastolic flow was significantly lower in HCM than in the controls (1.85+/-0.66 vs 3.18+/-1.62 m/s2, p<0.03). This abnormal response might be due to an increase in the reverse systolic flow and a decrease in the diastolic flow, probably caused by a slow acceleration of early diastolic flow velocity in the LAD.

Phasic coronary flow pattern and flow reserve in patients with left bundle branch block and normal coronary arteries

OBJECTIVES

The purpose of this study was to determine whether scintigraphic myocardial perfusion defects in patients with left bundle branch block (LBBB) and normal coronary arteries are related to abnormalities in coronary flow velocity pattern and/or coronary flow reserve.

BACKGROUND

Septal or anteroseptal defects on exercise myocardial perfusion scintigraphy are common in patients with LBBB and normal coronary arteries.

METHODS

Thirteen patients (7 men, age 61+/-8 years) with LBBB and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In all patients and in 11 control subjects coronary blood flow parameters were calculated from Doppler measurements of flow velocity in the left anterior descending coronary artery (LAD) before and after adenosine administration.

RESULTS

The time to maximum peak diastolic flow velocity was significantly longer both for the seven patients with (134+/-19 ms) and for the six without (136+/-7 ms) exercise perfusion defects than for controls (105+/-12 ms, p < 0.05), whereas the acceleration was slower (170+/-54, 186+/-42 and 279+/-96 cm/s2, respectively, p < 0.05). Coronary flow reserve in the patients with exercise perfusion defects (2.7+/-0.3) was significantly lower than in those without (3.7+/-0.5, p < 0.05) or in the control group (3.4+/-0.5, p < 0.05).

CONCLUSIONS

Patients with LBBB have an impairment of early diastolic blood flow in the LAD due to an increase in early diastolic compressive resistance resulting from delayed ventricular relaxation. Furthermore, exercise scintigraphic perfusion defects in these patients are associated with a reduced coronary flow reserve, indicating abnormalities of microvascular function in the same vascular territory.

Effect of ventricular pacing on coronary blood flow in patients with normal coronary arteries

Although ventricular pacing is thought to produce impairment of left ventricular function by altering the sequence of ventricular activation and AV dyssynchrony, little is known about the effect of ventricular pacing on coronary blood flow. We measured coronary blood flow and coronary flow reserve in the left anterior descending coronary artery during sinus rhythm, and during both atrial and ventricular pacing at a rate of 100 ppm in 14 patients with normal coronary arteries. The double product increased significantly during both types of pacing. Coronary arterial diameter during ventricular pacing significantly increased compared to that during both sinus rhythm and atrial pacing. Coronary flow velocity during ventricular pacing was significantly lower compared to that during both sinus rhythm and atrial pacing. Coronary blood flow increased significantly during atrial pacing (30.7% +/- 12.1%; P < 0.001), but not significantly during ventricular pacing (23.6% +/- 47.0%; P = ns). While coronary flow reserve during both atrial (3.9 +/- 1.3) and ventricular pacing (3.8 +/- 0.9) was lower compared to its value during sinus rhythm (4.5 +/- 1.5), the difference was not significant. There was a significant positive correlation between the coronary flow reserve during sinus rhythm and the increase of coronary blood flow during ventricular pacing (R2 = 0.78; P < 0.001). We concluded that an increase in coronary blood flow during ventricular pacing is not a common finding regardless of the increase in metabolic demand. The increase of coronary blood flow during ventricular pacing was less in patients with a reduced coronary flow reserve. These findings suggest that preservation of AV synchrony and the presence of a normal sequence of ventricular activation may play an important role in preserving coronary blood flow in this subset of patients.

Changes in phasic coronary blood flow velocity profile and relative coronary flow reserve in patients with hypertrophic obstructive cardiomyopathy

BACKGROUND

In this study, we both investigated coronary flow velocity in hypertrophic obstructive cardiomyopathy (HOCM) and tested the hypothesis of differing coronary flow reserve (CFR) of coronary arteries perfusing left ventricular regions with nonuniform myocardial hypertrophy by measuring the relative CFR.

METHODS AND RESULTS

Coronary flow velocity was assessed in left anterior descending coronary (LAD) and left circumflex (LCX) arteries in 18 patients with HOCM and marked hypertrophy only in the ventricular septum, in 13 patients without obstruction (HCM), and in 9 age- and sex-matched normal subjects at rest, during rapid atrial pacing, and after dobutamine infusion (5 to 30 microg/kg per minute). Relative CFR was estimated as the ratio between absolute CFR of the LAD and absolute CFR of the LCX (LAD/LCX(CF)). At the peak of rapid atrial pacing and during dobutamine stress, LAD/LCX(CF) was reversed in HOCM patients (from 1.25+/-0.11 to 0.82+/-0.07 and 0.79+/-0.06, respectively), whereas it remained unchanged in control subjects (from 1.0+/-0.1 to 1.0+/-0.05 and 1.0+/-0.05, respectively; P<.001). In HCM patients, LAD/LCX(CF) at rest was 1.10+/-0.11, whereas during rapid atrial pacing and dobutamine stress, it was 0.92+/-0.08 and 0.90+/-0.09, respectively. Relative CFR was 0.62+/-0.05 in HOCM patients and 1.05+/-0.05 (P<.001) in normal subjects. There was an inverse correlation between relative CFR and peak systolic outflow tract gradient (r2=.74, P<.001).

CONCLUSIONS

Regional distribution of hypertrophy in some patients with HOCM resulted in regional impairment of coronary flow. Relative CFR can be used to estimate regional disturbances of coronary flow and may help in patient selection for new interventional therapeutic techniques.

Coronary back flow pressure is elevated in association with increased left ventricular end-diastolic pressure in humans

To clarify the effect of left ventricular (LV) diastolic pressure on the coronary pressure-flow relation in humans, the instantaneous diastolic coronary pressure-Doppler flow velocity relation was analyzed at rest and during papaverine-induced maximal vasodilation in 15 patients with angiographically normal coronary arteries. The values for slope (alpha PF) and zero-flow pressure intercept (Pzf index) of the instantaneous diastolic coronary pressure-flow velocity relation were obtained by a linear regression analysis. Although alpha PF did not correlate with LV end-diastolic pressure (EDP), the Pzf index correlated positively with LVEDP both at rest and during maximal vasodilation (r = 0.64, P < 0.05 and r = 0.58, P < 0.05, respectively). Thus, the back pressure to coronary inflow, as indicated by the Pzf index, may be elevated in patients with increased LVEDP, resulting in the rightward shift of the maximally dilated coronary pressure-flow relation and decreased maximal coronary flow and reserve at any given perfusion pressure.

Effects of heart rate on coronary circulation and external mechanical efficiency in elderly hypertensive patients with left ventricular hypertrophy

BACKGROUND AND HYPOTHESIS

Mechanisms of heart failure in elderly hypertensive patients with hypertrophy have not been studied sufficiently. We hypothesized that impaired increment of coronary blood flow in response to increases in heart rate could be responsible for the occurrence or aggravation of heart failure.

METHODS

To test this hypothesis, we measured coronary hemodynamics and lactate balance during basal conditions and atrial pacing in 21 elderly patients aged > or = 65 years (mean 74 +/- 6 years) without coronary arterial disease: 7 normotensive control patients (Group 1), 7 hypertensive hypertrophic patients without a history of congestive heart failure (Group 2), and 7 patients with such history (Group 3). Coronary sinus blood flow (CSBF) was measured in coronary sinus using a thermodilution catheter.

RESULTS

During basal conditions, heart rate did not differ among the three groups (67 +/- 3 in Group 1, 65 +/- 11 in Group 2, and 63 +/- 6 beats/ in Group 3). CSBF was significantly higher in the two hypertrophic groups than in the control group, but CSBF normalized by left ventricular mass was significantly lower in both hypertrophic groups. External mechanical efficiency (EME) obtained as left ventricular work divided by myocardial oxygen consumption did not differ among groups during basal conditions (36 +/- 9% in Group 1, 35 +/- 8% in Group 2, and 29 +/- 9% in Group 3, NS). During atrial pacing to increase heart rate by 25 +/- 5% (lower) and 54 +/- 6% (higher), the increases in CSBF were markedly limited in both hypertrophic groups, and the response in Group 3 was more depressed than that in Group 2. EME did not change in the control group or in Group 2, but did decrease to 21 +/- 5% in Group 3 during the higher pacing rate (p < 0.01 vs. basal conditions). In this group, the relationship between EME and heart rate showed a significant negative correlation (r = -0.56, p = 0.02). Lactate balance in coronary sinus blood showed a tendency to production in Group 3 during the higher pacing rate, suggesting myocardial ischemia.

CONCLUSION

These findings suggest that in hypertensive hypertrophic patients with a history of heart failure, the coronary circulation system is vulnerable to increasing heart rate. In medical treatment of elderly hypertensive patients, control of heart rate in addition to blood pressure control should be considered to minimize the occurrence or aggravation of heart failure.