| Changes in carrying amount of goodwill |
The change in the carrying amount of goodwill by segment for the six-month period ended June 30, 2025 is detailed as follows (in thousands): | | | | | | | | | | | | 2025 | | | Cardiovascular | | Endoscopy | | Total | Goodwill balance at January 1 | | $ | 446,514 | | $ | 16,997 | | $ | 463,511 | Effect of foreign exchange | | | 2,758 | | | — | | | 2,758 | Additions and adjustments as the result of acquisitions | | | 38,286 | | | — | | | 38,286 | Goodwill balance at June 30 | | $ | 487,558 | | $ | 16,997 | | $ | 504,555 |
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| Other intangible assets |
Other intangible assets at June 30, 2025 and December 31, 2024 consisted of the following (in thousands): | | | | | | | | | | | | June 30, 2025 | | | Gross Carrying | | Accumulated | | Net Carrying | | | Amount | | Amortization | | Amount | Patents | | $ | 33,078 | | $ | (13,786) | | $ | 19,292 | Distribution agreements | | | 3,250 | | | (3,031) | | | 219 | License agreements | | | 12,595 | | | (9,608) | | | 2,987 | Trademarks | | | 51,456 | | | (26,233) | | | 25,223 | Customer lists | | | 62,676 | | | (38,214) | | | 24,462 | Total | | $ | 163,055 | | $ | (90,872) | | $ | 72,183 |
| | | | | | | | | | | | December 31, 2024 | | | Gross Carrying | | Accumulated | | Net Carrying | | | Amount | | Amortization | | Amount | Patents | | $ | 31,489 | | $ | (12,824) | | $ | 18,665 | Distribution agreements | | | 3,250 | | | (2,994) | | | 256 | License agreements | | | 11,557 | | | (9,125) | | | 2,432 | Trademarks | | | 47,613 | | | (24,177) | | | 23,436 | Customer lists | | | 57,933 | | | (36,223) | | | 21,710 | Total | | $ | 151,842 | | $ | (85,343) | | $ | 66,499 |
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| Estimated amortization expense |
Estimated amortization expense for developed technology and other intangible assets for the next five years consisted of the following as of June 30, 2025 (in thousands): | | | | Year ending December 31, | | Estimated Amortization Expense | Remaining 2025 | | $ | 45,989 | 2026 | | | 81,813 | 2027 | | | 78,208 | 2028 | | | 76,670 | 2029 | | | 65,166 |
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