**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Nerea Mora-Ayestarán, Hospital Universitario Puerta de Hierro, Madrid, Spain

**Main Body of the Abstract**
Background: Patients with ATTR-CM can exhibit left ventricular outflow tract obstruction (LVOTO) and mid-cavity level obstruction (MVO) mimicking Hypertrophic cardiomyopathy. Little is known about ATTR-CM and LVOTO/MVO and the impact of obstruction in prognosis.
Methods: We analyzed the prevalence of LVOTO/MVO among patients with ATTR-CM evaluated at Hospital Universitario Puerta de Hierro (Madrid, Spain) from March 2008 to July 2022. Obstruction was defined as an intracardiac gradient ≥30 mmHg at rest or with provocation.
Results: LVOTO/MVO was present in 11 patients (82% male, 78.8±9.2 years, 100% ATTRwt, 82% NYHA II/III) out of 417 ATTR-CM patients (2.64%) evaluated. Eight patients had LVOTO and 3 MVO. Mean gradients at rest and with Valsalva provocation were 38±37mmHg (Range: 10-140) and 52±16 mmHg (Range: 32-80), respectively. Among the 9 patients who had ≥2 echocardiograms, only 2 individuals exhibited persistent obstruction in all echocardiograms. Four patients received treatment with betablockers and dysopiramide for LVOTO. In 3, treatment was early discontinued (median 1.7 months) due to side effects and lack of improvement. Patient who maintained disopyramide showed transient mild improvement. No patient underwent septal reduction therapy. After a median follow-up of 15.2 months (IQR 7.4-54), 1 patient developed worsening heart failure and 2 had died. In a multivariate analysis adjusted by gender, age, LVEF, NAC stage, NYHA, and diuretic dose, the presence of LVOTO/MVO was not associated with mortality (HR 1.19, p=0.77).
Conclusion: LV obstruction is a rare finding in patients with ATTR-CM and is frequently dynamic. Obstruction was not associated with a worse prognosis.



**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Nerea Mora-Ayestarán, Hospital Universitario Puerta de Hierro, Madrid, Spain

**Main Body of the Abstract**
**Background:** Patients with ATTR-CM can exhibit left ventricular outflow tract obstruction (LVOTO) and mid-cavity level obstruction (MVO) mimicking Hypertrophic cardiomyopathy. Little is known about ATTR-CM and LVOTO/MVO and the impact of obstruction in prognosis.
**Methods:** We analyzed the prevalence of LVOTO/MVO among patients with ATTR-CM evaluated at Hospital Universitario Puerta de Hierro (Madrid, Spain) from March 2008 to July 2022. Obstruction was defined as an intracardiac gradient ≥30 mmHg at rest or with provocation.
**Results:** LVOTO/MVO was present in 11 patients (82% male, 78.8±9.2 years, 100% ATTRwt, 82% NYHA II/III) out of 417 ATTR-CM patients (2.64%) evaluated. Eight patients had LVOTO and 3 MVO. Mean gradients at rest and with Valsalva provocation were 38±37mmHg (Range: 10-140) and 52±16 mmHg (Range: 32-80), respectively. Among the 9 patients who had ≥2 echocardiograms, only 2 individuals exhibited persistent obstruction in all echocardiograms. Four patients received treatment with betablockers and dysopiramide for LVOTO. In 3, treatment was early discontinued (median 1.7 months) due to side effects and lack of improvement. Patient who maintained disopyramide showed transient mild improvement. No patient underwent septal reduction therapy. After a median follow-up of 15.2 months (IQR 7.4-54), 1 patient developed worsening heart failure and 2 had died. In a multivariate analysis adjusted by gender, age, LVEF, NAC stage, NYHA, and diuretic dose, the presence of LVOTO/MVO was not associated with mortality (HR 1.19, p=0.77).
**Conclusion:** LV obstruction is a rare finding in patients with ATTR-CM and is frequently dynamic. Obstruction was not associated with a worse prognosis.



Left Ventricular Obstruction in Transthyretin amyloid cardiomyopathy PC66 (#381)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.